## Trigonometry (11th Edition) Clone

Write $I$ in terms of the sine function: $$I=k-k\sin^2\theta$$
$$I=k\cos^2\theta$$ The exercise asks to write $I$ in terms of the sine function. This can be done by changing $\cos\theta$ into $\sin\theta$. Using Pythagorean Identity: $$\cos^2\theta=1-\sin^2\theta$$ we can rewrite $I$ as follows: $$I=k(1-\sin^2\theta)$$ $$I=k-k\sin^2\theta$$