Mathematics for IGCSE & O level - Angles (Section 2 - No. 25)
If three lines intersect at a point, and two angles are 120° and 70°, what is the value of the third angle?
50°
60°
70°
170°
설명
The sum of angles at a point is 360°. Subtract the known angles from 360° to find the missing angle: 360 - 120 - 70 = 170, but the missing one is the third angle, 360-120-70=170, 360-170*2=20