Найдите 4cos2x , если sinx=-0,5

Question

Найдите 4cos2x , если sinx=-0,5

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Answer 1

tgaob=6

 

 

4cos2x   sinx= -0.5

cos2x=1-sin^2x=1-(-0.5)^2=1-0.25=0.75

4cos2x=4*0.75=3

Answer 2

sin^x = 0,25
cos^x = 1 - 0,25 = 0,75

cos2x = cos^x - sin^x
4cos2x = 4(0,75 - 0,25) = 2