- #1

skyturnred

- 118

- 0

## Homework Statement

The point is (0, -8, 0)

r≥0

0≤θ≤2∏

0≤[itex]\varphi[/itex]≤∏

## Homework Equations

## The Attempt at a Solution

So here is what I've done so far:

I know that r=8 because x and z are 0

I know that θ=∏/4 or 3∏/4, but which one? both of these satisfy the following equation (which is the only one I know for this)

cos(θ)=y/x

Also, I am confused about [itex]\varphi[/itex]. I know that:

tan([itex]\varphi[/itex])=y/x, but y is negative, and x is zero. I know the value of arctan(∞) as well as arctan(-∞) but which one do I use? I am so confused. Thanks!