Find all solutions in the interval [ 0,20pi] to the equation

Question

Sin(x/10)cos(x/10) = 1/4

Answer 1

Let θ = x / 10

sin θ cos θ = (1/2)(sin 2θ)

1 / 4 = (1/2)(sin 2θ)

1 / 2 = sin 2θπ

π / 6 = 2θ

π / 12 = θ

π / 12 = x / 10

10 π / 12 = x

5 π / 6 = x

You determine other values in stated domain.