If θ is an acute angle of a right triangle, then the value of

sin θ cos(90° - θ) + cos θ sin (90° - θ) is

1. 0

2. 2 sin θ cos θ

3. 1

4. 2 sin² θ

Since, θ is an acute angle triangle,

cos(90° - θ) = sin θ and sin(90° - θ) = cos θ.

Using above values in sin θ cos(90° - θ) + cos θ sin (90° - θ) we get,

⇒ sin θ sin θ + cos θ cos θ
⇒ sin² θ + cos² θ
⇒ 1.

Hence, Option 3 is the correct option.