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Trigonometric identities

Trigonometry equalities, inequalities and expressions - sin, cos, tan, cot
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Trigonometric identities

Postby ken_165 » Sun Jun 17, 2018 7:58 pm

In the equation, it says that: cos2x=cos^2x-sin^2x=2cos^2x-1... Now, why is 2cos^2x-1 is used?
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Re: Trigonometric identities

Postby Math Tutor » Mon Jun 18, 2018 2:08 am

[tex]\sin^2x+\cos^2x = 1[/tex]
Therefore [tex]\sin^2x = 1- \cos^2x[/tex]

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