standard_description: Derive the formula A = 1/2 ab sin(C) for the area of a triangle by drawing an auxiliary line from a vertex perpendicular to the opposite side.
problem_activity: $${\overline{AD} \parallel \overline{BC}}$$
and
$${\angle EJB}$$
is supplementary to
$${\angle JBK}$$
. Prove that
$${\overline {AD} \parallel \overline{JE}}$$
.
[IMG]


aligns: no