cos x = 12 1 s i n 2 x + co s 2 x = 1 s i n 2 x + ( 12 1 ) 2 = 1 s i n 2 x + 144 1 = 1 s i n 2 x = 1 − 144 1 s i n 2 x = 144 144 − 144 1 s i n 2 x = 144 143 s in x = 144 143 s in x = 12 143
t an 2 x = cos 2 x s in 2 x s in 2 x = 2 s in x cos x ; cos 2 x = co s 2 x − s i n 2 x s in 2 x = 2 ⋅ 12 143 ⋅ 12 1 = 144 2 143 cos 2 x = ( 12 1 ) 2 − ( 12 143 ) 2 = 144 1 − 144 143 = − 144 142 t an 2 x = 144 2 143 : ( − 144 142 ) = − 144 2 143 ⋅ 142 144 = − 71 143
Given cos x = 12 1 and 0"> sin x > 0 , we find that tan 2 x = − 71 143 . This is derived through trigonometric identities and relationships. The calculations involve finding sin x before applying the double angle formulas for sine and cosine.
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