Simplify the expression by using a DoubleAngle Formula or a

Simplify the expression by using a Double-Angle Formula or a Half-Angle Formula.

(a) 2 sin(11°) cos(11°)

(b) 2 sin(4) cos(4)

Solution

2sin(11 ^*)cos(11^*)

= sin(22^*)

using the identity

sin2A = 2sinAcosA

Similarly
2sin(4@)cos(4@) = sin(8@)

using same identity