# math

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cos2x-sinx=0. Factor and solve for sinx

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1 - 2sin^2 x - sinx = 0
2sin^2 x + sinx - 1 = 0
(2sinx - 1)(sinx + 1) = 0
sinx = 1/2 or sinx = -1

in degrees, x = 30° , 150° , 270°
in radians, x = π/5 , 5π/6 , 3π/2

• math -

Thanks. I was wondering, why is it "+ sin x" in the second step?

• math -

do you just change all the signs of the terms? if so, why is this necessary?

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I multiplied each term by -1
(notice all the signs have switched)

It just makes it easier to factor.

• math -

ok thank you.

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