The minimum value of 4sin2 θ + 5cos2 θ is?

1 -4 0 4

4

4sin2 θ + 5cos2 θ ⇒ 4sin2 θ + 4cos2 θ + cos2 θ ⇒ 4 + cos2 θ since cos2 θ > 0 ; minimum value occurs when cos2 θ = 0 ∴ minimum value = 4