ABC is an isosceles triangle in which AB = AC. Side BA is produced to D such that AD = AB. Find angle BCD

*let m∠cob = 50°30’, m∠aob = 70° and m∠aoc = 20°30’. could point c be in the interior of ∠aob? why?

If t8 = 4 and t12 = −2, find the first three terms of the arithmetic sequence.

If the angle bisectors of a pair of opposite angles of a quadrilateral are the opposite sides of a parallelogram formed by the two angle bisectors and two sides of the quadrilateral, is the quadrilateral always a parallelogram? explain your answer.