1.

Which of the following expression equals cos 20 for all θ e R ?a) 1+2 sin20 b) cos0 +sino-2 sin20d) 2 cos0+ 11 - 2 sin

Answer»

cos2θ=cos²θ-sin²θ=2cos²θ-1=1-2sin²θ

thanks

cos20=cos0-sin0=2cos0-1=1-2sin0



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