### Home > PC > Chapter 11 > Lesson 11.1.2 > Problem 11-23

11-23.

In the diagram at right, the point*P*has Cartesian coordinates (*x*,*y*) and polar coordinates (*r*,*θ*). Homework Help ✎Explain why

*x*=*r*cos*θ*.Find

*y*in terms of*r*and θ.Find

*r*in terms of*x*and*y*.Find

*θ*in terms of*x*and*y*.

Using the diagram, cos(*θ*) = *x*/*r*.

Using the diagram, sin(*θ*) = ?

What theorem can be used to relate the three sides of a right triangle?

Use tangent.