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Q. 16

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Calculus
Found in: Page 464
Calculus

Calculus

Book edition 1st
Author(s) Peter Kohn, Laura Taalman
Pages 1155 pages
ISBN 9781429241861

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Short Answer

Why is it okay to use a triangle without thinking about the unit circle when simplifying expressions that result from a trigonometric substitution with x = a sin u or x = a tan u? Why do we need to think about the unit circle after trigonometric substitution with x = a sec u?

Ans: Quadrants came into account as the resultant absolute values are significant since tanu is positive for u in the first quadrant and negative for u in the second quadrant. That's why in this case unit circle is considered.

See the step by step solution

Step by Step Solution

Step 1. Given information:

x = a sin ux = a tan u

Step 2. Solving the trigonometric substitution:

In the trigonometric substitution of x=asinu and x=atanu, the choice of quadrant will never be an issue. That's why the unit circle is never considered. But in the trigonometric substitution of x=asecu, quadrants came into account as the resultant absolute values are significant since tanu is positive for u in the first quadrant and negative for u in the second quadrant. That's why in this case unit circle is considered.

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