The green triangle is potentially a copy of the small red triangle, but rotated 180 deg around the green circle labeled "Rotation Axis". Imagine the green circle as a spindle on a turntable, and then rotate the red triangles around it.
The yellow dotted line and triangle are a completely separate idea from the green objects. The yellow dotted line is a mirror axis, where the small red symmetric triangle is connected end-to-end with the yellow , with nearly identical high/low test points.
This is not advice. I do not give advice. You do not want my advice.