GEOMETRY PROOFS HELP NEEDED ASAP!!!!!!!

I have three proofs to write and I'm just so confused as to where to start:

1) Prove that the base angles of an isosceles triangle are congruent. Be sure to create and name the appropriate geometric figures.
2) Prove the diagonals of a parallelogram bisect one another. Be sure to create and name the appropriate geometric figures.
3)Write an indirect proof proving the two non-right angles of a right triangle measure less than 90°.

Question

GEOMETRY PROOFS HELP NEEDED ASAP!!!!!!!

I have three proofs to write and I'm just so confused as to where to start:

1) Prove that the base angles of an isosceles triangle are congruent. Be sure to create and name the appropriate geometric figures.
2) Prove the diagonals of a parallelogram bisect one another. Be sure to create and name the appropriate geometric figures.
3)Write an indirect proof proving the two non-right angles of a right triangle measure less than 90°.