Question

The peak value of cos (wt + 60°) - sin (wt - 30°) is
1. 1
2. √2
3. 2
4. √3

Answer 1

Correct Answer - Option 3 : 2

Let x(t) = cos (wt + 60°) - sin (wt - 30°)

= cos (90 + (wt - 30°)) - sin (wt - 30°)

From trigonometric identity, cos (90° + θ) = - sin θ 

So, x(t) = - sin (wt - 30°) - sin (wt - 30°)

= - 2 sin (wt - 30°)

Therefore, peak value of x(t) is 2.

cos (90° + θ) = - sin θ 

sin (90° + θ) = cos θ