Question

If sinθ = A, find cos(π/2-θ)

(using trigonometric identities to fine the value)

Answer 1

Cos(π/2 - θ) = A

Explanation:

We know that:

Sin(θ) = A

And we want to find the value of Cos(π/2 - θ)

Here we can use the cosine relationship:

Cos(a - b) = Cos(a)*Cos(b) + Sin(A)*Sin(B)

Then:

Cos(π/2 - θ) = Cos(π/2)*Cos(θ ) + Sin(π/2)*Sin(θ)

We know that:

Cos(π/2) = 0

Sin(π/2) = 1

Then:

Cos(π/2 - θ) = Cos(π/2)*Cos(θ ) + Sin(π/2)*Sin(θ) = 0*Cos(θ ) + 1*Sin(θ)

= 1*Sin(θ) = A

Cos(π/2 - θ) = A