A tent in the shape of a triangular prism is made using the following piece of fabric

In the figure below, segment ac is congruent to segment ab: triangle abc with a segment joining vertex a to point d on side bc. side ab is congruent to side ac which statement is used to prove that angle abd is congruent to angle acd? segment ad bisects angle cab. triangle acd is similar to triangle abd. segment ad is congruent to segment ac. angle cab is congruent to angle cba.

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.

Find the maximum value of p= 4x + 5y subject to the following constraints :