The above drawing is used for cutting incline a pipe, if we have large diameter of pipe and want to cut with certain angle we will have difficulties to make the similar incline of each pipe side. To make have similar angle we should make a drawing first with the same scale with the object.
The Y value is get from the line of each point on the circle that cut on the triangle side, from this point will get of Y value as on Y-axis. X value is the value from pipe diameter, on this example pipe have diameter 10 without unit, the unit is up to you. From the calculation we get the circle of this pipe 31.4 so the half of circle is 15.7.
On the projection drawing we get just a half part of the circle, so we draw the other half part just copy from the result but mirror value. Like on the table example above. For this calculation you can download this excel calculation here: Expanse