Diagram shows a shaft with brass segment A B of length 1800 millimeters which is connected to aluminum segment B C of length 800 millimeter using a flange at B and a torque T of 50 Newton meter is applied on C. The x axis is taken along the axis of the cylinders and the y axis is taken along the rigid support at A and perpendicular to the x axis.

The rotation angle of C relative to support A is the sum of the angles of twist in segments (1) and (2):

ϕC=ϕ1+ϕ2