How the Omni angle cut page frames knee bracing
The fetched Omni angle cut calculator treats the problem as a right-triangle knee bracing layout. Once you know any two outer dimensions, you can solve the third with the Pythagorean theorem and then determine both cut angles.
Core angle cut formulas
C = sqrt(A^2 + B^2)
alpha = arccos(A / C)
beta = 90 deg - alpha
C_A = t / tan(alpha)
C_B = t / tan(beta)
Sample from the source article
Omni's worked example uses a 10 cm plank with A = 40 cm and C = 60 cm. That gives alpha about 48.19 deg, beta about 41.81 deg, and marking offsets of roughly 8.94 cm and 11.18 cm on the plank faces.