Dacla wants to know how to determine the polar coordinate $.$ What should Katarina tell Dacia?

"Use $=tan-1(\frac{x}{y})."$

"Use $=tan(\frac{y}{x})."$

"Use the formula $r=\sqrt[\phantom{2}]{x2+y2}."$

"Use $=tan-1(\frac{y}{x})."$

Katarina is correct. Note that Dacia must use the signs of $x$ and $y$ to find on which quadrant the point lies.