Trigonometric Functions & Identities

Asked by  | 20th Jun, 2008, 11:14: AM

Expert Answer:

squuare both the sides  we will have cos220 +sin220-2 sin20 cos 20 =p2

now cos220 +sin220=1  and 2 sin20 cos 20 =sin 40

so sin 40 = 1-p2

that is cos40 = (1 - sin240)1/2 =  (2p2 - p4)1/2

Answered by  | 10th Aug, 2008, 04:08: PM

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