To rotate a triangle 90 degrees clockwise, take each of the triangle's three coordinates (x, y), flip them and make the x negative (y, -x). You need graph paper, a separate sheet of paper and two different-colored pens or pencils.

**Write down the triangle's original coordinates**Plot the original coordinates on a graph. Connect the points to form a triangle. Label the points of the triangle as A, B and C. On a separate sheet of paper, write down the x and y coordinates of points A, B and C as (x, y).

**Flip the coordinates, and make the x negative**On your list of coordinates, write down the flipped coordinates of points A, B and C as (y, x). Make each x coordinate of the flipped coordinates negative by placing the negative symbol next to it.

**Plot the flipped coordinates**Use a different-colored pen or pencil than the one that was used to plot the original triangle, and plot the flipped version of point A. Label the point as A. Plot the flipped version of point B. Label the point as B. Plot the flipped version of point C. Label the point as C. Connect the points to form a triangle.