= √ (A 2+B 2) {[A/√ (A 2+B 2) * COSA]+B/√ (A 2+B 2) * Sina}

=√(a^2+b^2)sin(A+B)

Let a/√ (a 2+b 2) = sinb, b/√ (a 2+b 2) = cosb, and such an angle is unique in a period.

Acosa+BSINA = √ (A 2+B 2) SIN (A+B)，B = ARCTAN (A/B)。