Question

Minimum value of $5si{n}^2\theta +4co{s}^2\theta$ is

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The correct option is D

4

Let $f\left(\theta \right)$ = $5si{n}^2\theta +4co{s}^2\theta$ = $4+si{n}^2\theta$

∴ $f\left(\theta \right)$ $\ge$ 4 + 0 ($\because si{n}^2\theta \ge 0$)

∴ The minimum value of $f\left(\theta \right)$ is 4.