standard_description: Prove the addition and subtraction formulas for sine, cosine, and tangent and use them to solve problems.
problem_activity: Given:
$${BC=7}$$
,
$${\overleftrightarrow{AD}}$$
bisects
$${\angle BAC}$$
Find: measure of
$${BD}$$
and the measure of
$${DC}$$
[IMG]


aligns: no