Q311
If P + Q + R = 60°, then what is the value of cosQcosR(cosP - sinP) + sinQsinR(sinP - cosP)?
A.
Answer
B.
C.
D.
Answer: Option A
Solution
Answer: Option A
Solution:
∵ P + Q + R = 60°By putting P = 0°, Q = 0° and R = 60°
⇒ cosQcosR(cosP - sinP) + sinQsinR(sinP - cosP)
⇒ 1 × cos60°(cos0° - sin0°) + sin0°.sin60°(sin0° - cos0°)
⇒ (1 - 0) + 0
⇒