Question

Найдите 4cos2x если sinx=-0,5

Answer 1

sin^2x+cos^2x=1

sin^2x=1/4

cos^2x=1-sin^2x=1-1/4=3/4

4*cos2x=4*(cos^2x-sin^2x)=4*(3/4-1/4)=4*(1/2)=2

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