Solve:- (sin 31°/cos59°)² +(cos59°/sin31°)² - 4 sin2 45°
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Answer:
sin(90°-α) = cosα
cos(90°-α) = sinα
so,
cos70°/sin20° + cos59°/sin31° -8 sin²30°
=[cos(90°-20)]/sin20° + [cos(90°-31°)]/sin31° - 8×(1/2)²
=sin20°/sin20° + sin31°/sin31° - 2
= 1+1- 2
= 0
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