# Thread: Using sin and cos to rotate a point

1. ## Using sin and cos to rotate a point

Hello. Im trying to move a point in 2D space. If i apply a rotation to the point, and then try to move it again, i want it to move along the axis defined in its local space insted of the 'world' space.

Ive been told i can do this by using the angle im rotating the point by like so :-
pos.X += Cos(rotate)
pos.Y += Sin(rotate)

this will make any movements along the x axis correct. Its similar for Y, i just have to swap the Cos and Sin around. The only probly is, im not sure why this works. Anyone know why? I hope i managed to explain it clearly enough!

2. Originally Posted by Cubed2D
Hello. Im trying to move a point in 2D space. If i apply a rotation to the point, and then try to move it again, i want it to move along the axis defined in its local space insted of the 'world' space.

Ive been told i can do this by using the angle im rotating the point by like so :-
pos.X += Cos(rotate)
pos.Y += Sin(rotate)

this will make any movements along the x axis correct. Its similar for Y, i just have to swap the Cos and Sin around. The only probly is, im not sure why this works. Anyone know why? I hope i managed to explain it clearly enough!