Answer
$(2.25, 4.35)$
Work Step by Step
Solve for $r$ using the formula $r=\sqrt {x^{2}+y^{2}}$ to obtain:
$$r=\sqrt {(-0.8)^{2}+(-2.1)^{2}}=2.25$$
Use the formula $\alpha=\tan^{-1}(\frac{y}{x})$ to find the reference angle:
$$\alpha=\tan^{-1}\left(\frac{-2.1}{-0.8}\right)=1.21$$
Since $(-0.8,-2.1)$ is in the third quadrant, then
$$\theta=\alpha+\pi=1.21+3.14=4.35$$
Thus, the polar coordinates for the point $(-0.8,-2.1)$ is $(2.25, 4.35)$.
