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Question
Prove that:
cos 30° . cos 60° - sin 30° . sin 60° = 0
Sum
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Solution
LHS=cos 30°. cos 60° - sin 30°. sin 60°
= `(sqrt3)/(2) (1)/(2) – (1)/(2) (sqrt3)/(2) = (sqrt3)/(4) – (sqrt3)/(4) = 0 = RHS`
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Chapter 21: Trigonometrical Ratios [Sine, Consine, Tangent of an Angle and their Reciprocals] - EXERCISE 21 (C) [Page 322]
