<PAGE>   1
                                                                    EXHIBIT 10.2
                                                                    ------------
     

                          OPTION ACCELERATION AGREEMENT
                          -----------------------------

     OPTION ACCELERATION AGREEMENT, dated as of September 15, 1997, by and
between MathSoft, Inc. (the "Company") and Robert P. Orlando (the "Officer").

     WHEREAS, the Officer has made and is expected to continue to make major
contributions to the Company;

     WHEREAS, the Company desires continuity of management; and

     WHEREAS, the Officer is willing to continue to render services to the
Company subject to the conditions set forth in this Agreement.

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the Company and the Officer agree
as follows:

     1. CHANGE OF CONTROL. Upon a Change in Control, the Company shall:

     (a) Cause 50% of any unexercisable installments of any stock options held
by the Officer on the Change of Control that have not expired to become
exercisable on the Change of Control; PROVIDED, HOWEVER, that such acceleration
of exercisability shall not occur to the extent that: (i) the Change of Control
is intended to be accounted for as a pooling of interests; and (ii) the Company
concludes, after consulting with its independent accountants, that such
acceleration would prevent the Change of Control transaction from being
accounted for as a pooling of interests for financial accounting purposes; and

     (b) Cause the period after a termination of employment within which any
option may be exercised by the Officer in accordance with the provisions of the
relevant option agreement and option plan to be extended to twelve months;
PROVIDED, HOWEVER, that such extension of exercisability shall not occur to the
extent that: (i) the Change of Control is intended to be accounted for as a
pooling of interests; and (ii) the Company concludes, after consulting with its
independent accountants, that such extension of exercisability would prevent the
Change of Control transaction from being accounted for as a pooling of interests
for financial accounting purposes.

PROVIDED, HOWEVER, that: (i) the Company's obligation to provide any of the
amounts and benefits set forth in this Section 1 shall be subject to, and
conditioned upon, the Officer's execution, on or before the Change of Control,
of a full release of claims satisfactory to the Company releasing the Company
and its affiliates, subsidiaries, divisions, directors, employees and agents
from any claims arising from or related to the Officer's employment or severance
from employment with the Company, including any claims arising from this
Agreement, such release to be substantially in the form of EXHIBIT A hereto (the
"Release"); and (ii) notwithstanding any other provision of this Agreement, the
Company shall not be obligated to 

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                                      -2-


provide any of the amounts and benefits set forth in this Section 1 until any
applicable period within which the Officer may revoke the Release has expired.

     2. GENERAL.

     (a) For purposes of this Agreement, "Change of Control" shall mean the
closing of: (i) a merger, consolidation, liquidation or reorganization of the
Company into or with another Company or other legal person, after which merger,
consolidation, liquidation or reorganization the capital stock of the Company
outstanding prior to consummation of the transaction is not converted into or
exchanged for or does not represent more than 50% of the aggregate voting power
of the surviving or resulting entity; (ii) the direct or indirect acquisition by
any person (as the term "person" is used in Section 13(d)(3) or 14(d)(2) of the
Securities Exchange Act of 1934, as amended) of more than 50% of the voting
capital stock of the Company, in a single or series of related transactions;
(iii) the sale, exchange, or transfer of the business unit for which the Officer
principally works; or (iv) the sale, exchange, or transfer of all or
substantially all of the Company's assets (other than a sale, exchange or
transfer to one or more entities where the stockholders of the Company
immediately before such sale, exchange or transfer retain, directly or
indirectly, at least a majority of the beneficial interest in the voting stock
of the entities to which the assets were transferred).

     (c) Notwithstanding anything to the contrary in this Agreement, if the
Company determines in its sole discretion after consultation with its tax and
accounting advisors that the Officer is a Disqualified Individual (as defined in
Section 280G of the Internal Revenue Code of 1986, as amended (the "Code")) and
that any portion of any payment or distribution by the Company to or for the
benefit of the Officer, whether paid or payable or distributed or distributable
pursuant to the terms of this Agreement or otherwise (a "Payment") would be an
Excess Parachute Payment (as defined in Section 280G of the Code) but for the
application of this sentence, then the amount of all such Payments otherwise
payable to the Officer pursuant to this Agreement shall be reduced to the
minimum extent necessary (but in no event to less than zero) so that no portion
of any Payment, as so reduced, constitutes an Excess Parachute Payment. For
purposes of this reduction, no portion of any Payment shall be taken into
account to the extent that such Payment, in the opinion of the Company, after
consultation with its tax and accounting advisors, does not constitute a
"parachute payment" within the meaning of Section 280G(b)(2) of the Code.

     (d) Except as otherwise provided herein, this Agreement shall be binding
upon and inure to the benefit of the Company and any successor (whether direct
or indirect, by purchase, merger, consolidation, reorganization or otherwise) of
the Company; PROVIDED, HOWEVER, that the Company shall obtain the written
agreement of any successor (whether direct or indirect, by purchase, merger,
consolidation, reorganization or otherwise) of the Company to be bound by the
provisions of this Agreement as if such successor were the Company and for
purposes of this Agreement, any such successor of the Company shall be deemed to
be the "Company" for all purposes.


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                                      -3-


     (e) Nothing in this Agreement shall create any obligation on the part of
the Company or any other person to continue the employment of the Officer.

     (f) Nothing herein shall affect the Officer's obligations under any key
employee, non-competition, confidentiality, option or similar agreement between
the Company and the Officer currently in effect or which may be entered into in
the future.

     (g) This Agreement shall be governed by and construed in accordance with
the laws of the Commonwealth of Massachusetts. This Agreement constitutes the
entire Agreement between the Officer and the Company concerning the subject
matter hereof and supersedes any prior negotiations, understandings or
agreements concerning the subject matter hereof, whether oral or written, and
may be amended or rescinded only upon the written consent of the Company and the
Officer. The invalidity or unenforceability of any provision of this Agreement
shall not affect the other provisions of this Agreement and this Agreement shall
be construed and reformed to the fullest extent possible. The Officer may not
assign any of his/her rights or obligations under this Agreement; the rights and
obligations of the Company under this Agreement shall inure to the benefit of,
and shall be binding upon, the successors and assigns of the Company. This
Agreement may be executed in any number of counterparts, all of which taken
together shall constitute one and the same instrument.

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                                      -4-


     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed as of the date first written above.


                                             The Company:
                                             ------------

                                             MATHSOFT, INC.

                                             By: /s/ Charles J. Digate
                                                 -------------------------------

                                             Name: Charles J. Digate

                                             Title: President and C.E.O.


                                             The Officer:
                                             ------------

                                             Signature: /s/ Robert P. Orlando
                                                        ------------------------

                                             Printed Name:  Robert P. Orlando





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                                                                       EXHIBIT A

                                AGREEMENT/WAIVER


     It is hereby agreed by and between ____________________ (the "Officer") and
MathSoft, Inc. (the "Company"), for good and sufficient consideration more fully
described below, that:

     1. CONSIDERATION. The Company will provide the Officer with the amounts and
benefits described in Section 1 of the Option Acceleration Agreement entered
into by the Company and the Officer, dated ___________, 1997 (the "Acceleration
Agreement"), subject to the terms and conditions of such Acceleration Agreement.
The Officer understands that all such benefits are conditioned upon the Officer
signing this Agreement.

     2. SETTLEMENT OF AMOUNTS DUE THE OFFICER. The Officer agrees that the
benefits set forth above in Section 1, together with any amounts previously
provided to the Officer by the Company, shall be complete and unconditional
payment, settlement, satisfaction and accord with respect to all obligations and
liabilities of the Company and any of its affiliated companies (including their
respective successors, assigns, shareholders, officers, directors, employees
and/or agents) to the Officer, and all claims, causes of action and damages by
the Officer against the Company and/or any such other parties regarding the
Officer's employment with and termination from employment with the Company,
including, without limitation, all claims for back wages, salary, draws,
commissions, bonuses, vacation pay, equity compensation, expenses, compensation,
severance pay, attorney's fees, compensatory damages, exemplary damages, or
other costs or sums.

     3. RELEASE.

     (a) In exchange for the amounts and benefits described in Section 1 and
other good and valuable consideration, receipt of which is hereby acknowledged,
the Officer and his/her representatives, agents, estate, successors and assigns,
absolutely and unconditionally hereby release and forever discharge the Company,
its affiliated companies and/or their successors, assigns, directors,
shareholders, officers, employees and/or agents, both individually and in their
official capacities, (the "Releasees"), from any and all actions or causes of
action, suits, claims, complaints, contracts, liabilities, agreements, promises,
debts and damages, whether existing or contingent, known or unknown, which arise
out of the Officer's employment with or termination from employment with the
Company. This release is intended by the Officer to be all encompassing and to
act as a full and total release of any claims that the Officer may have or has
had against the Releasees, including, but not limited to, any federal, state or
local law or regulation dealing with either employment or employment
discrimination such as those laws or regulations concerning discrimination on
the basis of age, race, color, religion, creed, sex, sexual orientation,
national origin, ancestry, marital status, physical or mental disability, any
veteran status or any military service or application for any military service;
any contract, whether oral or written, express or implied; or common law.


<PAGE>   6
                                       A-2


     (b) The Officer agrees not only to release and discharge the Releasees from
any and all claims as stated above that the Officer could make on his/her own
behalf or on behalf of others, but also those claims which might be made by any
other person or organization on behalf of the Officer, and the Officer
specifically waives any right to become, and promises not to become, a member of
any class in a case in which a claim or claims against the Releasees are made
involving any matters which arise out of the Officer's employment with or
termination from employment with the Company. Nothing in this Agreement is to be
construed as an admission by the Releasees of any liability or unlawful conduct
whatsoever.

     4. WAIVER OF RIGHTS AND CLAIMS UNDER THE AGE DISCRIMINATION AND EMPLOYMENT
ACT OF 1967. [Only applicable if the Officer is 40 years of age or older at the
time of termination of employment.]

     (a) The Officer has been informed that since he/she is 40 years of age or
older, he/she has or might have specific rights and/or claims under the Age
Discrimination and Employment Act of 1967. In consideration for the amounts
described in Section 1 hereof, the Officer specifically waives such rights
and/or claims to the extent that such rights and/or claims arose prior to the
date this Agreement was executed.

     (b) The Officer was advised by the Company of his/her right to consult with
an attorney prior to executing this Agreement.

     (c) The Officer was further advised when he/she was presented by the
Company with the original draft of this Agreement on _______, 199_, that he/she
had at least 21 days within which to consider its terms and to consult with or
seek advice from an attorney or any other person of his/her choosing, until the
close of business on __________, 199_.

     5. CONFIDENTIALITY. The Officer agrees he/she shall not divulge or publish,
directly or indirectly, any information whatsoever regarding the substance,
terms or existence of the Acceleration Agreement or this Agreement and/or any
discussions or negotiations relating to the Acceleration Agreement or this
Agreement to any person or organization, except to his/her immediate family
members, counsel or accountant, and unless required under law or court order.

     6. REPRESENTATIONS AND GOVERNING LAW.

     (a) This Agreement represents the complete and sole understanding between
the parties, supersedes any and all other agreements and understandings, whether
oral or written, except for the [list key employee, non-competition, option or
confidentiality agreements] entered into by the Company and Officer, and the
Acceleration Agreement, which remain in full force and effect. This Agreement
may not be modified, altered or rescinded except upon written consent of the
Company and Officer. The invalidity or unenforceability of any provision of this
Agreement shall not affect the other provisions of this Agreement, but this
Agreement shall be revised, construed and reformed to the fullest extent
possible to effectuate the purposes of this Agreement. This Agreement shall be
binding upon and inure to the benefit of the Company and the Officer and their
respective heirs, successors and assigns. The parties agree that the

<PAGE>   7
                                       A-3


Company will not have an adequate remedy if the Officer fails to comply with
Sections 3, 4, and 5 hereof and that damages will not be readily ascertainable,
and that in the event of such failure, the Officer shall not oppose any
application by the Company requiring a decree of specific performance or an
injunction enjoining a breach of this Agreement. If the Officer breaches any of
his/her obligations hereunder, he/she shall forfeit all right to payments
pursuant to Section 1.

     (b) This Agreement shall be governed by and construed in accordance with
the laws of the Commonwealth of Massachusetts, without giving effect to the
principles of conflicts of law thereof.

     (c) The Officer represents that he/she has read the foregoing Agreement,
fully understands the terms and conditions of such Agreement, and is voluntarily
executing the same. In entering into this Agreement, the Officer does not rely
on any representation, promise or inducement made by the Releasees, with the
exception of the consideration described in this document.

     7. EFFECTIVE DATE. [Only applicable if the Officer is 40 years of age or
older at the time of termination of employment.] The Officer may revoke this
Agreement during the period of seven (7) days following its execution by the
Officer, and this Agreement shall not become effective or enforceable until this
revocation period has expired.




<PAGE>   8
                                       A-4




                                  The Company:
                                  ------------

                                  MATHSOFT, INC.

                                  By: ______________________________________

                                  Name: ____________________________________

                                  Title: ___________________________________

                                  Date: ____________________________________


                                  The Officer:
                                  ------------

                                  Signature: _______________________________

                                  Printed Name: ____________________________

                                  Date: ____________________________________