Paul M. answered • 6d

BS Mathematics, MD

I don't understand the hint!

If ∠A = 40 degrees and ∠B = 60 degrees and ∠C is the third angle in the triangle, then ∠C must be 100 degrees since the sum of th angles in a triangle is 180 degrees.

Of course the hint is the way you prove that the sum of the angles in a triangle is 180 degrees (and note that you have used the parallel postulate to prove this).