first part of mathmo question for intersection of circles and lines
a bit more work on answer formatting
fixing the code that prints the circle equations

apparently I can’t do powers in JavaScript correctly *facepalm*
fixed answers, and some printing improvements to the circles and lines intersections questions
slight tweaks to formatting of circle equations

In equations of the form x^2-2ax+y^2-2bx=C, if C is negative, then it gets put on the other side as x^2-2ax+y^2-2bx-C=0
added helper function to simplify surds of the form (a+b sqrt c)/d

This is handy for the circle/square intersection questions, which often have messy answers which we need to simplify.
finished mathmo question for circle/line intersections
tweaked parameters for circle and line equation questions
basic structure for mathmo question about circle/circle intersections
finished mathmo question on circle/circle intersections

This commit covers the case of two intersections, along with pretty printing of answers. It also adds the appropriate unit tests, and corrects those broken in the last commit (by the updated geometry helpers).

Note that mathmo may fail if you’ve used the circle/line intersection question (introduced in commit b48fc41). This had the topicID C44, which has been renamed to C34. Solution is to clear the local storage.
fixed formatting bugs in makeFurtherVector

Specifically, I’ve switched to bold face for the vectors (consistent with the other questions) and tidied up a misplaced comma that I introduced.

Unit tests updated appropriately.
fixed make matrix transformations mathmo questions

The problem was the use of `-sines[a]` and `-cosines[a]`, which were returning NaN errors.

I’ve introduced objects acosines[] and asines[] which should do exactly what we want, but don’t break this way.
switch to pmatrix environment for matrices

Unit tests updated also.
removed double brackets on fmatrix
fixed syntax bug introduced in fractions.js
fixed broken e variable and other minor typos

Also typos for those fixes.
fixing a typo in the answer of parallel/perpendicular lines

In the perpendicular case, if the intercept of the answer was zero, then the equation printed would be

y=mx0
Merge pull request #24 from alexwlchan/master

mathmo questions on circle/line intersections