1.

(cos2 67。-sin, 23°)虱册靭君?What is the value of (cos 67 -sin2 239)?

Answer»

cos²67-sin²23=?

cos(90-α)=sin(α)cos(90-23)=sin(23)cos(67)=sin(23)

on squaring both sides

cos²67=sin²23cos²67-sin²23=0



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