Posted by **Lynn** on Friday, March 23, 2012 at 9:46pm.

sin^2x/cosx=sec^2x-1

- precal -
**Reiny**, Saturday, March 24, 2012 at 12:52am
sin^2x /cosx = 1/cos^2 x - 1

multiply each side by cos^2 x

sin^2 x cosx = 1 - cos^2x

(1 - cos^2x)cosx = 1 - cos^2x

cosx - cos^3x - 1 + cos^2x = 0

cos^3x - cos^2x - cosx + 1 = 0

cos^2x(cosx - 1) -(cosx - 1) = 0

(cosx-1)(cos^2x-1) =0

(cosx-1)(cosx-1)(cosx+1) = 0

cosx = 1 or cosx = -1

x = 0, 2π or x = π

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