## Calculus 8th Edition

$$\theta =\frac{\pi}{4}$$ or $$\theta =\frac{5\pi}{4}$$
$$x=y$$ Here, $$x=rcosθ$$, and $$y=rsinθ$$ $$rcosθ=rsinθ$$ $$cosθ=sinθ$$ $$\frac{sin \theta}{cos \theta} =1$$ $$tan \theta =1$$ $$\theta =\frac{\pi}{4}$$ or $$\theta =\frac{5\pi}{4}$$