16Hit1600
Geometry and TrigonometryVery hardRelationship between sine and cosine of complementary angles

Geometry and Trigonometry practice question

In right triangle PQR, angle R is the right angle and sin P = 0.6. What is cos Q?

  1. A. 0.6Correct
  2. B. 0.8
  3. C. 0.4
  4. D. 1.2

Answer: A. 0.6

Angles P and Q are complementary (P + Q = 90°), and the sine of an angle equals the cosine of its complement: cos Q = sin P = 0.6.

Why the other answers are wrong

B. 0.8
0.8 is cos P (or sin Q), the other ratio.
C. 0.4
0.4 is 1 − 0.6; sine and cosine of complements are equal, not complements of each other.
D. 1.2
1.2 is not possible for a cosine (at most 1).

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