Science:Math Exam Resources/Courses/MATH101/April 2010/Question 03 (d)
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Question 03 (d) 

FullSolution Problem. Justify your answer and show all your work. Simplification of the answer is not required. Evaluate the following integral: Hint: Use a substitution and interpret the result as an area. 
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 hint below. Consider it for a while. Does it give you a new idea on how to approach the problem? If so, try it! 
Hint 

Try the substitution . 
Checking a solution serves two purposes: helping you if, after having used the hint, you still are stuck on the problem; or if you have solved the problem and would like to check your work.

Solution 

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Please rate my easiness! It's quick and helps everyone guide their studies. Following the hint, we try the substitution . Then and the endpoints will change to and . Hence
This last value can be seen to be half the area of a quarter circle of radius 9. Hence, the value is
as required. 