Evaluate \(\int_7^9\)cos⁡(x)dx.

Category: QuestionsEvaluate \(\int_7^9\)cos⁡(x)dx.
Editor">Editor Staff asked 11 months ago

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
NCERT Solutions for Subject Clas 12 Math Select the correct answer from above options 
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1 Answers
Editor">Editor Staff answered 11 months ago

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)