# calculus

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prove
cos squared B- sin squared B= 2cos squared B -1

• calculus -

cos^2 B - sin^2 B = 2cos^ B - 1

LS
= cos^2 B - (1 - cos^2 B)
= 2cos^2 B - 1
= RS

• calculus -

substitute 1 - cos^2B for sin^2 B

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