Question

Evaluate: $\underset{\frac{\pi }{4}}{\overset{\frac{\pi }{2}}{\int }}cos2xdx$

• A. $\frac{1}{4}$
• B. $\frac{1}{2}$
• C. $-\frac{1}{4}$
• D. $-\frac{1}{2}$

Answer 1

Answer: (D)

We have, $I={\int }_{\frac{\pi }{4}}^{\frac{\pi }{2}}cos2xdx$
${\left[\frac{sin2x}{2}\right]}_{\frac{\pi }{4}}^{\frac{\pi }{2}}=-\frac{1}{2}$