How to rotate a triangle in an equation

[tomallan]

Hi,

i have a set of definition for a triangle shape:

-3/4<x<3/4

-x/sqrt(3) + sqrt(3)/4 < y < x/sqrt(3) +sqrt(3)/4

The centroid of this triangle is at 0,0

i want to rotate this triangle by a certain degree from the centroid but i am not sure how, because if i just multiply it by cos or sin of the angle, it will just become smaller.

any hints will be appreciated.

 

[da_nang]

Any point can be rotated around the origin by rotating the coordinate system.