Mitrofan's Angle Formula
Find Z. Z=90°-F, F=X-Y.
Demonstration:
1. N+X+Z=180°
2. Z=180°-X-N
3. N=90°-Y
4. Replace N in 2. above
5. Z=180°-X-(90°-Y) =180°-X-90°+Y = 90°-X+Y