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Some Applications of Trigonometry
Question
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Write the value of sin2 69° + sin2 21°. 

Answer

sin2 69° + sin2 21° = sin2 (90 - 21°) + sin2 21°
= cos2 21° +sin2 21° = 1. 1

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Some More Questions From Some Applications of Trigonometry Chapter

Choose the correct option and justify your choice:
sin 2A = 2 sin A is true when A = 
(A) 0°         (B) 30°         (C) 45°       (D) 60°