Question

Evaluate \(\int_7^9\)cos⁡(x)dx.

(a) 8 (-sin 9 – sin 7)

(b) 8 (sin 9 + sin 7)

(c) 8 (sin 9 – sin 7)

(d) 7 (sin 9 – sin 7)

I had been asked this question by my college director while I was bunking the class.

This question is from Definite Integral topic in portion Integrals of Mathematics – Class 12

Answer 1

Right answer is (c) 8 (sin 9 – sin 7)

The best I can explain: \(\int_7^9\)8cos⁡(x)dx = 8 \(\int_7^9\)cos⁡(x)dx

= 8 (cos x)^97

= 8 (sin 9 – sin 7)