Question

PLEASE HELP WITH SOME GEOMETRY

Prove the following statement by contradiction using an indirect proof. In a triangle angle A = 90°, then the triangle is a right triangle. Which of the following choices would be the first step to temporarily assume?
angle A = 90°
the triangle is a right triangle
the triangle is not a right triangle
angle A is not 90°

Answer 1

The contradiction proof should start with a negation:
"The triangle is not a right triangle angle and A is not 90°"
Then you proof that this statement is false