I have a point at 0,0,0(the origin).

And I have an object that will move around that point.

The following data is given for that object:

r = 5

theta=4

phi=6

phi is the angle that is between y and z.

theta is(probably) between y and z.

To find the object coordinates(x,y,z),the following equations are given:

y = r * cos(phi)

x = r * sin(phi) * sin(theta)

z = -r * sin(phi) * cos (theta)

we use -r on z because theta is measured counterclockwise from -z.

As you can see the equations above make an object stay at some certain coordinates away from the origin. Everything is solved,the only problem is that I don't understand it.

I understand how we get y,but the x and z are sci fi for me,I mean why does x use sin on both phi and theta and z uses sin and cos?

Take it easy on me,I suck at math,and in the last 3 days I've been trying to understand those equations.If you know why everything is like that,please explain with as many details as you can,so I can finally understand and sleep...