express \cos^4\theta in terms of powers of \tan\theta and \cos\theta.
pls help on the above problem, thanks
Hello, lawochekel!
A slightly different approach . . .
$\displaystyle \text{Express }\cos^4\theta\text{ in terms of powers of }\tan\theta\text{ and }\cos\theta.$
$\displaystyle \cos^4\!\theta \;=\;\cos^2\!\theta\cdot\cos^2\!\theta \;=\;\frac{\cos^2\!\theta}{\sec^2\!\theta} \;=\;\frac{\cos^2\!\theta}{\tan^2\!\theta + 1}$