**Cos 2 Pi**. Note that the cosine function is able to recognize some special angles and make the calculations with. And the complex conjugate of algebraic is algebraic (in fact it's just another $n$th root of unity), so add it to its conjugate because also the sum of two algebraics is algebraic.

Welcome to Precalculus II, a derivative work of Jay Abramson. And the complex conjugate of algebraic is algebraic (in fact it's just another $n$th root of unity), so add it to its conjugate because also the sum of two algebraics is algebraic. For all values of angle A and B `(i)sin(A-B)=sinAcosB-cosAsinB (ii)sin(A+B)=sinAcosB+cosAsinB`.

### For all values of angle A and B `(i)sin(A-B)=sinAcosB-cosAsinB (ii)sin(A+B)=sinAcosB+cosAsinB`.

Welcome to Precalculus II, a derivative work of Jay Abramson.

And the complex conjugate of algebraic is algebraic (in fact it's just another $n$th root of unity), so add it to its conjugate because also the sum of two algebraics is algebraic. Geometric representation of sine and cosine of angles. Note that the cosine function is able to recognize some special angles and make the calculations with.