16Hit1600
Geometry and TrigonometryVery hardAngle between two angle bisectors

Geometry and Trigonometry practice question

In triangle PQR, angle P measures 50° and angle Q measures 60°. The bisectors of angles Q and R meet at point I. What is the measure, in degrees, of angle QIR?

Answer: 115

Angle R is 70°. In triangle QIR the angles at Q and R are half of 60° and 70°, so angle QIR = 180 − 30 − 35 = 115.

Common wrong answers

If you answered 25
25 is half of angle P.
If you answered 65
65 is 30 + 35, the two half-angles.
If you answered 130
130 is angle Q plus angle R without halving.

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