The obvious solution is to change the axis of rotation to the bottom of the triangle. There’s no way to do that, but there is a workaround. In a nutshell, copy the triangle and rotate it ...

Enlarge the triangle ABC by a scale factor of \(\frac{1}{2}\) about the centre of enlargement O. First, draw ray lines from O to each corner of the triangle. Next, measure the distance from O to ...