posted by anon .
cos2x-sinx=0. Factor and solve for sinx
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
Thanks. I was wondering, why is it "+ sin x" in the second step?
do you just change all the signs of the terms? if so, why is this necessary?
I multiplied each term by -1
(notice all the signs have switched)
I like my quadratics to start with a positive coefficient, although that would not be necessary.
It just makes it easier to factor.
ok thank you.