Precalculus: Mathematics for Calculus, 7th Edition

Half-Angle, $\pm\sqrt{\frac{1-\cos u}{2}}$
If we know the value of $\cos x$ and the quadrant in which $x/2$ lies, we can find the value of $\sin(x/2)$ by using the Half-Angle Formula for Sine. State the formula: $\sin(x/2)=\pm\sqrt{\frac{1-\cos u}{2}}$.