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Question 05 (a) 

Evaluate . A calculatorready answer is sufficient. 
Make sure you understand the problem fully: What is the question asking you to do? Are there specific conditions or constraints that you should take note of? How will you know if your answer is correct from your work only? Can you rephrase the question in your own words in a way that makes sense to you? 
If you are stuck, check the hints below. Read the first one and consider it for a while. Does it give you a new idea on how to approach the problem? If so, try it! If after a while you are still stuck, go for the next hint. 
Hint 1 

Consider the substitution and use an appropriate trigonometric identity. 
Hint 2 

(For the alternative solution) Use integration by parts, using . Use the trig identity to have an expression with only powers of the sine function move all the terms with the highest power to the same side. repeat the process until you get an easy integral you can solve. 
Checking a solution serves two purposes: helping you if, after having used all the hints, you still are stuck on the problem; or if you have solved the problem and would like to check your work.

Solution 1 

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Please rate my easiness! It's quick and helps everyone guide their studies. Recall and the Pythagorean Identity . Consider the substitution . We observe that as ranges from to , the function ranges from to . Moreover, and by the Pythagorean Identity,
Plugging this into the integral and applying the substitution, we get
The last equality follows from that is an even function. Finally, we evaluate the integral as follows. 
Solution 2 

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Please rate my easiness! It's quick and helps everyone guide their studies. (Alternative solution) Using integration by parts , we pick , which yields
Using the trig identity , we have
Thus, . We now compute using integration by parts with , and so . Using the same trigonometric identity we have . Using we get Answer: 