solve for x 2 Sin^2X + 2 SinX CosX - 1= 0
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Dear william, use the following identity:
Hello, william! You should be familiar with these identities: . . . . Solve for We have: . . . . . . . . . . Therefore: .
Originally Posted by william solve for x 2 Sin^2X + 2 SinX CosX - 1= 0 sin 2x = 2 sin x cos x and cos 2x = cos2x - sin2x = 1 - 2 sin2x so 2 sin2x + 2 sin x cos x -1 = 0 is equivalent to sin 2x - cos 2x = 0 which is sin 2x = cos 2x or tan 2x = 1. therefore, in the first quadrant, 2x is 45o
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