**M4A+**

This is very much like Method 1, in that we have again constructed a parallel line, this time parallel to a green line.

This produces a new angle adjacent to the give angle v, of size u [corresponding angles].

Altogether the adjacent angles u and v are equal to the given right-angle [alternate angles].

Thus u + v = 90˚, so v = 90˚ – u.

This produces a new angle adjacent to the give angle v, of size u [corresponding angles].

Altogether the adjacent angles u and v are equal to the given right-angle [alternate angles].

Thus u + v = 90˚, so v = 90˚ – u.