Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 7 - No. 22)
If you know two angles of a triangle, can you determine the third angle?
No
Yes, if the triangle is right-angled.
Yes, the sum of angles is 180 degrees.
Only if it's an isosceles triangle.
Explanation
The sum of angles in any triangle is 180 degrees.