91Ó°ÊÓ

Show that 2 cis \(60^{\circ}\) and 2 cis \(\left(-60^{\circ}\right)\) are conjugates.

Show that if \(z=\cos \theta-i \sin \theta\), then \(|z|=1\)

Let \(\sin A=3 / 5\) with \(A\) in QI and \(\sin B=5 / 13\) with \(B\) in QI and find\(\cos (A+B)\)

Simplify each expression to a single trigonometric function.\(\cos 30^{\circ} \cos 90^{\circ}-\sin 30^{\circ} \sin 90^{\circ}\)

Is addition of complex numbers a commutative operation? That is, if \(z_{1}\) and \(z_{2}\) are two complex numbers, is it always true that \(z_{1}+z_{2}=z_{2}+z_{1}\) ?

Find \(\sin \theta\) and \(\cos \theta\) if the given point lies on the terminal side of \(\theta\). \((3,-4)\)

Solve triangle \(A B C\) if \(A=73.1^{\circ}, b=243 \mathrm{~cm}\), and \(c=157 \mathrm{~cm}\)