### Home > PC > Chapter 5 > Lesson 5.2.1 > Problem5-51

5-51.

u2 − 4u = 3u2
u3 − 3u2 − 4u = 0
u(u2 − 3u − 4) = 0
u(u − 4)(u + 1) = 0
u = 0, u = 4, u = −1
But u ≠ 0 because you would have division by zero.

u = sinθ
−1 = sinθ

$\theta=270\degree \text{ or } \frac{3\pi}{2}$

u = sinθ
4 = sinθ