# Math Help - Converting to polar (easy)

1. ## Converting to polar (easy)

I'm converting -3,4 to polar.

I have come up with r = +/ 5

And tan (x) = -4/3

When I do x = arctan (-4/3)
in my calculator I get -.927 but the book has 2.214

Why?

Thanks.

2. ## Re: Converting to polar (easy)

Originally Posted by minneola24
I'm converting -3,4 to polar.
Let $\theta = \pi + \arctan \left( {\frac{{ - 4}}{3}} \right)$

Then the polar form of $(-3,4)$ is $(5\cos(\theta),5\sin(\theta))~.$

3. ## Re: Converting to polar (easy)

I'm confused why your adding pie,

And the book has 5,2.21. And -5, 5.356. As answers

4. ## Re: Converting to polar (easy)

Originally Posted by minneola24
I'm confused why your adding pie,
And the book has 5,2.21. And -5, 5.356. As answers
Have a look at this webpage. You will see the reply is correct.

The point $(-3,5)\in II$ and ${\frac{-\pi}{2}<\arctan \left( {\frac{{ - 4}}{3}} \right)}<0$ therefore adding $\pi$ gives the correct second quadrant angle.