What's wrong with my math?

I'm trying to make this blue box orbit the red box using Cos & Sin, however the distance between the boxes is increasing.

Why? Shouldn't it stay the same distance away?

capx

You want the angle you put into cos, and sin to be the same, and a value between 0, and 360. Use a variable and implement a counter to add to that variable.

Also you want to use the object that you want to rotate around as the x, and y.

Sprite.X+Cos(yourvariable)*distance(self.x,self.y,sprite.x,sprite.y)

Sprite.Y+Sos(yourvariable)*distance(self.x,self.y,sprite.x,sprite.y)

Then set yourvariable using the variable + something *dt.

Note it will probably work if you go beyond 360, but you can always use %360 as a limiter.

But aren't the angles for sin & cos the same in my capx?

You used angle(), but you need that to either increase, or decrease.

The reason the distance was increasing is because on every single tick it moves in a straight line that is 90 degrees from the direction to the centre.. In a sense it's not truly curved, the angle is just corrected 60 times a second.

Imagine what happens on a single tick, and if that distance was 200 pixels instead.. i think that makes it easier to see why it's moving further away from centre.. i hope .. I can totally understand the confusion though.

edit: you should try something like this, it's more or less what newt was saying.

<img src="https://dl.dropbox.com/u/53374990/Forum/orbit.png" border="0" />