Rotating when the Center of Rotation is (-1,2)

Question

I have to rotate a right triangle( doesn’t matter if i rotate it clockwise or counter clockwise) at the point (-1,2) and i can’t. The first point,X, is (-2,3). The next point,Y,(4,3). And the last point ,Z,(4,7). Help

Answer 1

Do you want the size of the triangle?

Do you want the size of three circles?

From which angle is the rotation?

Answer 2

First, translate the center of rotation to (0,0)

So, (-1, 2) → (-1+1, 2-2) = (0, 0)

Translate each vertex of the triangle the same way:

So, X = (-2,3) → (-2+1, 3-2) = (-1, 1) = X'

Rotate X' about the origin (say 90° counterclockwise) to get (-1, -1) [(x,y) → (-y,x)]

Then, undo the original translation (instead of adding 1 to x, subtract 1 and instead of subtracting 2 from y, add 2)

(-1, -1) → (-1 - 1, -1 + 2) = (-2, 1)

Follow the same steps for Y and Z.