If A = B = 45°, show that :
sin (A - B) = sin A cos B - cos A sin B
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If A = 30°, then prove that :
2 cos2 A - 1 = 1 - 2 sin2 A
sin 3A = 3 sin A - 4 sin3 A
cos (A + B) = cos A cos B - sin A sin B
If 2sin A - 1 = 0 and A is an acute angle, the measure of angle A is :
30°
45°
60°
90°