If cos(θ)=3/5, and θ is in Quadrant I, then what is sin(θ/2)?

Answer 1

The half-angle formula is sin(x/2) = sqrt[(1-cos x)/2].

Answer 2

Use half angle formula:

Sin(θ/2) = ±√((1 - Cos(θ))/2)

Since you are told θ is in the first quadrant we need to consider only the positive solution

= √((1 - 3/5)/2) = √(1/5) = 0.4472