SOLUTIONS TO DIFFERENTIATION OF INVERSE TRIGONOMETRIC FUNCTIONS



SOLUTION 1 : Differentiate tex2html_wrap_inline416. Apply the product rule. Then

tex2html_wrap_inline418

tex2html_wrap_inline420

(Factor an x from each term.)

tex2html_wrap_inline424 .

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SOLUTION 2 : Differentiate tex2html_wrap_inline426 . Apply the quotient rule. Then

tex2html_wrap_inline428

tex2html_wrap_inline430

tex2html_wrap_inline432

tex2html_wrap_inline434

tex2html_wrap_inline436 .

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SOLUTION 3 : Differentiate tex2html_wrap_inline438arctex2html_wrap_inline440arctex2html_wrap_inline442 . Apply the product rule. Then

tex2html_wrap_inline444arctex2html_wrap_inline446arctex2html_wrap_inline448arctex2html_wrap_inline450arctex2html_wrap_inline442

tex2html_wrap_inline454arctex2html_wrap_inline456arctex2html_wrap_inline442

= ( arctex2html_wrap_inline462arctex2html_wrap_inline464 .

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SOLUTION 4 : Let tex2html_wrap_inline466arctex2html_wrap_inline468 . Solve f'(x) = 0 for x . Begin by differentiating f . Then

tex2html_wrap_inline476

tex2html_wrap_inline478

(Get a common denominator and subtract fractions.)

tex2html_wrap_inline480

tex2html_wrap_inline482

tex2html_wrap_inline484

tex2html_wrap_inline486

tex2html_wrap_inline488 .

(It is a fact that if tex2html_wrap_inline490 , then A = 0 .) Thus,

2(x - 2)(x+2) = 0 .

(It is a fact that if AB = 0 , then A = 0 or B=0 .) It follows that

x-2 = 0 or x+2 = 0 ,

that is, the only solutions to f'(x) = 0 are

x = 2 or x = -2 .

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SOLUTION 5 : Let tex2html_wrap_inline512 . Show that f'(x) = 0 . Conclude that tex2html_wrap_inline516. Begin by differentiating f . Then

tex2html_wrap_inline520 .

If f'(x) = 0 for all admissable values of x , then f must be a constant function, i.e.,

tex2html_wrap_inline528 for all admissable values of x ,

i.e.,

tex2html_wrap_inline532 for all admissable values of x .

In particular, if x = 0 , then

tex2html_wrap_inline538

i.e.,

tex2html_wrap_inline540 .

Thus, tex2html_wrap_inline542 and tex2html_wrap_inline516 for all admissable values of x .

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SOLUTION 6 : Evaluate tex2html_wrap_inline548 . It may not be obvious, but this problem can be viewed as a derivative problem. Recall that

tex2html_wrap_inline550

(Since h approaches 0 from either side of 0, h can be either a positve or a negative number. In addition, tex2html_wrap_inline556 is equivalent to tex2html_wrap_inline558. This explains the following equivalent variations in the limit definition of the derivative.)

tex2html_wrap_inline560

tex2html_wrap_inline562 .

If tex2html_wrap_inline564 , then tex2html_wrap_inline566, and letting tex2html_wrap_inline568, it follows that

tex2html_wrap_inline570

tex2html_wrap_inline572

tex2html_wrap_inline574

tex2html_wrap_inline576

tex2html_wrap_inline578

tex2html_wrap_inline580

tex2html_wrap_inline582

tex2html_wrap_inline584

tex2html_wrap_inline586 .

The following problems require use of the chain rule.

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SOLUTION 7 : Differentiate tex2html_wrap_inline588 . Use the product rule first. Then

tex2html_wrap_inline590

(Apply the chain rule in the first summand.)

tex2html_wrap_inline592

tex2html_wrap_inline594

(Factor out tex2html_wrap_inline596. Then get a common denominator and add.)

tex2html_wrap_inline598

tex2html_wrap_inline600

tex2html_wrap_inline602 .

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SOLUTION 8 : Differentiate tex2html_wrap_inline604 . Apply the chain rule twice. Then

tex2html_wrap_inline606

tex2html_wrap_inline608

(Recall that tex2html_wrap_inline610.)

tex2html_wrap_inline612

tex2html_wrap_inline614 .

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SOLUTION 9 : Differentiate tex2html_wrap_inline616 . Apply the chain rule twice. Then

tex2html_wrap_inline618

(Recall that tex2html_wrap_inline620.)

tex2html_wrap_inline622

tex2html_wrap_inline624

tex2html_wrap_inline626 .

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SOLUTION 10 : Determine the equation of the line tangent to the graph of tex2html_wrap_inline628 at x = e . If x = e , then tex2html_wrap_inline634, so that the line passes through the point tex2html_wrap_inline636. The slope of the tangent line follows from the derivative (Apply the chain rule.)

tex2html_wrap_inline638

tex2html_wrap_inline640

tex2html_wrap_inline642 .

The slope of the line tangent to the graph at x = e is

tex2html_wrap_inline646

tex2html_wrap_inline648

tex2html_wrap_inline650 .

Thus, an equation of the tangent line is

tex2html_wrap_inline652 .

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Duane Kouba
Tue Sep 16 16:10:59 PDT 1997