Question

Please help me!

Suppose a triangle has sides a,b, and c, and that a^2+b^2 > c^2. Let theta be the measure of the angle opposite the side length c. Which of the following must be true? Check all that apply.

A. theta is an acute angle.
B. The triangle is not a right triangle.
C. cos theta > 0
D. The triangle is a right triangle.

Please help me confirm that my answers are correct.

I've chosen B. because if it was a right triangle, then a^2+b^2 would not be greater than c^2 but equivalent, like in the Pythagorean Theorem, and from this reasoning I can eliminate answer D. because the a^2+b^2 must be equal to c^2 to be a right triangle. However, I'm not sure there are any other answers other than B.

Thanks for the help in advance!

Answer 1

I agree with you because theta could be acute or obtuse, and if obtuse, negative value.