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Basic Trigonometric Identities, Sums and Differences of angles, sin? 0 + cos'0 = 1, 1+ cot 0, sin a + B), = sin a cos B + cosa sin B, = cosec e, 0., sin a - B), = sina cos B -cosa sin B, tan' 0 +1, = sec? 0, cos a + B), = cosa cos B - sina sin B, cos a - B), cosa cos B + sin a sin B, Double Angles, tan a + tan B, = 2 sin 0 cos0, tan(a + B), sin 20, 1- tana tan B, tana – tan B, tan(a - B), = cos 0 – sin0, = 1-2 sin? 0, cos 20, 1+ tan a tan B, = 2cos? 0 – 1, > Triple Angles, 2 tan 0, tan 20, sin 30, = 3sin 0 – 4sin' 0, 1-2 tan? 0, cos 30, 4cos' 0 - 3cos0, sin 0, = }(1- cos 20), 3 tan 0 – tan'0, tan 30, cos 0, (1+ cos 20), 1-3 tan? 0