how do i prove (sin^4 x)-(cos^4 x)= (2sin^2x)-1

- Mar 21st 2010, 07:42 PMsomanyquestions[SOLVED] Verify that each trigonometric equation is an identity.
how do i prove (sin^4 x)-(cos^4 x)= (2sin^2x)-1

- Mar 21st 2010, 07:48 PMpickslides
- Mar 21st 2010, 07:51 PMsomanyquestions
- Mar 21st 2010, 08:05 PMStroodle
$\displaystyle \left [\sin^2 (x)\right ]^2-\left [ 1-\sin^2 (x)\right ]^2$

$\displaystyle =\left [sin^2(x)+(1-sin^2(x))\right ]\left [sin^2(x)-(1-sin^2(x))\right]$ - Mar 21st 2010, 08:13 PMsomanyquestions
- Mar 21st 2010, 08:16 PMpickslides
- Mar 21st 2010, 08:17 PMStroodle
That works too :)