16Hit1600
Geometry and TrigonometryVery hardAngle in a triangle with an altitude

Geometry and Trigonometry practice question

In triangle PQR, angle P measures 40° and angle Q measures 90°. An altitude is drawn from Q to side PR, meeting it at point S. What is the measure, in degrees, of angle SQR?

Answer: 40

Angle R = 180 − 40 − 90 = 50°. In right triangle QSR (right angle at S), angle SQR = 90 − 50 = 40°. (Equivalently, the altitude from the right angle creates triangles similar to the original.)

Common wrong answers

If you answered 45
45 assumes the altitude bisects the right angle, which it does only in an isosceles right triangle.
If you answered 50
50 is angle R (and angle PQS), not angle SQR.
If you answered 90
90 is angle Q as a whole; the altitude splits it into 50° and 40°.

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