Mathematics for IGCSE & O level - Pythagoras' Theorem And Trigonometry (Section 5 - No. 10)
If two angles of a triangle are 30° and 60°, what is the measure of the third angle?
30°
60°
90°
120°
Explication
The sum of angles in a triangle is 180 degrees. 180 - 30 - 60 = 90.