Hello thereddevilsFor (1), I assume you used the facts that(opp sides of a parallelogram)So the triangles are congruent, SAS.

(given)

(corresponding angles, )

For (2), a parallelogram is a rhombus if its diagonals are perpendicular. Well, can you see how to use a pair of equal angles in the congruent triangles to prove ? And you're given that , and . So that will be enough to prove is a rectangle, and therefore .

For (3), use the congruent triangles to show that . Also, , to show that .

Can you fill in all the details now?

Grandad