What am I doing wrong finding the derivative of $frac{3-x}{2}sqrt{1-2x-x^2}+2arcsin{frac{1+x}{sqrt{2}}}$?
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$$y=frac{3-x}{2}sqrt{1-2x-x^2}+2arcsin{frac{1+x}{sqrt{2}}}$$
For convenience, let
$$A=frac{3-x}{2}sqrt{1-2x-x^2},$$
$$B=2arcsin{frac{1+x}{sqrt{2}}}.$$
$$y'=A'+B'$$
$$A'=(-frac{1}{2})(sqrt{1-2x-x^2})+(-2x)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
$$A'=(-frac{1}{2})(sqrt{1-2x-x^2})+(-x)(frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
$$A'=(-frac{1-2x-x^2}{2sqrt{1-2x-x^2}})+(frac{x^2-3x}{{2sqrt{1-2x-x^2}}})$$
$$A'=(-frac{1-2x-x^2}{2sqrt{1-2x-x^2}})+(frac{x^2-3x}{{2sqrt{1-2x-x^2}}})$$
$$A'=frac{2x^2-x-1}{{2sqrt{1-2x-x^2}}}$$
$$B'=2bigg(arcsin{frac{1+x}{sqrt{2}}}bigg)'$$
$$B'=2 bigg( frac{1+x}{sqrt{2}} bigg)' bigg(arcsin{frac{1+x}{sqrt{2}}}bigg)'$$
$$B'=sqrt{2} bigg( frac{1}{sqrt{1- frac{1+2x+x^2}{2}} } bigg)$$
$$B'=sqrt{frac{4}{1-2x-x^2}}$$
$$B'=frac{4}{2sqrt{1-2x-x^2}}$$
$$y'=A'+B'=frac{2x^2-x+3}{2sqrt{1-2x-x^2}}$$
The answer in the book is
$$y'=frac{x^2}{sqrt{1-2x-x^2}}$$
calculus derivatives
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$$y=frac{3-x}{2}sqrt{1-2x-x^2}+2arcsin{frac{1+x}{sqrt{2}}}$$
For convenience, let
$$A=frac{3-x}{2}sqrt{1-2x-x^2},$$
$$B=2arcsin{frac{1+x}{sqrt{2}}}.$$
$$y'=A'+B'$$
$$A'=(-frac{1}{2})(sqrt{1-2x-x^2})+(-2x)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
$$A'=(-frac{1}{2})(sqrt{1-2x-x^2})+(-x)(frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
$$A'=(-frac{1-2x-x^2}{2sqrt{1-2x-x^2}})+(frac{x^2-3x}{{2sqrt{1-2x-x^2}}})$$
$$A'=(-frac{1-2x-x^2}{2sqrt{1-2x-x^2}})+(frac{x^2-3x}{{2sqrt{1-2x-x^2}}})$$
$$A'=frac{2x^2-x-1}{{2sqrt{1-2x-x^2}}}$$
$$B'=2bigg(arcsin{frac{1+x}{sqrt{2}}}bigg)'$$
$$B'=2 bigg( frac{1+x}{sqrt{2}} bigg)' bigg(arcsin{frac{1+x}{sqrt{2}}}bigg)'$$
$$B'=sqrt{2} bigg( frac{1}{sqrt{1- frac{1+2x+x^2}{2}} } bigg)$$
$$B'=sqrt{frac{4}{1-2x-x^2}}$$
$$B'=frac{4}{2sqrt{1-2x-x^2}}$$
$$y'=A'+B'=frac{2x^2-x+3}{2sqrt{1-2x-x^2}}$$
The answer in the book is
$$y'=frac{x^2}{sqrt{1-2x-x^2}}$$
calculus derivatives
1
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
– amWhy
Nov 22 at 22:24
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up vote
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$$y=frac{3-x}{2}sqrt{1-2x-x^2}+2arcsin{frac{1+x}{sqrt{2}}}$$
For convenience, let
$$A=frac{3-x}{2}sqrt{1-2x-x^2},$$
$$B=2arcsin{frac{1+x}{sqrt{2}}}.$$
$$y'=A'+B'$$
$$A'=(-frac{1}{2})(sqrt{1-2x-x^2})+(-2x)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
$$A'=(-frac{1}{2})(sqrt{1-2x-x^2})+(-x)(frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
$$A'=(-frac{1-2x-x^2}{2sqrt{1-2x-x^2}})+(frac{x^2-3x}{{2sqrt{1-2x-x^2}}})$$
$$A'=(-frac{1-2x-x^2}{2sqrt{1-2x-x^2}})+(frac{x^2-3x}{{2sqrt{1-2x-x^2}}})$$
$$A'=frac{2x^2-x-1}{{2sqrt{1-2x-x^2}}}$$
$$B'=2bigg(arcsin{frac{1+x}{sqrt{2}}}bigg)'$$
$$B'=2 bigg( frac{1+x}{sqrt{2}} bigg)' bigg(arcsin{frac{1+x}{sqrt{2}}}bigg)'$$
$$B'=sqrt{2} bigg( frac{1}{sqrt{1- frac{1+2x+x^2}{2}} } bigg)$$
$$B'=sqrt{frac{4}{1-2x-x^2}}$$
$$B'=frac{4}{2sqrt{1-2x-x^2}}$$
$$y'=A'+B'=frac{2x^2-x+3}{2sqrt{1-2x-x^2}}$$
The answer in the book is
$$y'=frac{x^2}{sqrt{1-2x-x^2}}$$
calculus derivatives
$$y=frac{3-x}{2}sqrt{1-2x-x^2}+2arcsin{frac{1+x}{sqrt{2}}}$$
For convenience, let
$$A=frac{3-x}{2}sqrt{1-2x-x^2},$$
$$B=2arcsin{frac{1+x}{sqrt{2}}}.$$
$$y'=A'+B'$$
$$A'=(-frac{1}{2})(sqrt{1-2x-x^2})+(-2x)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
$$A'=(-frac{1}{2})(sqrt{1-2x-x^2})+(-x)(frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
$$A'=(-frac{1-2x-x^2}{2sqrt{1-2x-x^2}})+(frac{x^2-3x}{{2sqrt{1-2x-x^2}}})$$
$$A'=(-frac{1-2x-x^2}{2sqrt{1-2x-x^2}})+(frac{x^2-3x}{{2sqrt{1-2x-x^2}}})$$
$$A'=frac{2x^2-x-1}{{2sqrt{1-2x-x^2}}}$$
$$B'=2bigg(arcsin{frac{1+x}{sqrt{2}}}bigg)'$$
$$B'=2 bigg( frac{1+x}{sqrt{2}} bigg)' bigg(arcsin{frac{1+x}{sqrt{2}}}bigg)'$$
$$B'=sqrt{2} bigg( frac{1}{sqrt{1- frac{1+2x+x^2}{2}} } bigg)$$
$$B'=sqrt{frac{4}{1-2x-x^2}}$$
$$B'=frac{4}{2sqrt{1-2x-x^2}}$$
$$y'=A'+B'=frac{2x^2-x+3}{2sqrt{1-2x-x^2}}$$
The answer in the book is
$$y'=frac{x^2}{sqrt{1-2x-x^2}}$$
calculus derivatives
calculus derivatives
asked Nov 22 at 22:17
fragileradius
297114
297114
1
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
– amWhy
Nov 22 at 22:24
add a comment |
1
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
– amWhy
Nov 22 at 22:24
1
1
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
– amWhy
Nov 22 at 22:24
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
– amWhy
Nov 22 at 22:24
add a comment |
3 Answers
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You got A' wrong.
$ A = frac{3-x}{2}cdot(sqrt{1-2x-x^2}) = fcdot g$
where: $ f =frac{3-x}{2} $ , $ g = sqrt{1-2x-x^2} $
$A'= f'g + g'f$
$ f'g = (-frac{1}{2})(sqrt{1-2x-x^2})$ is correct, but the second part is $ g'f = (-2x -2)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$ rather than
$(-2x)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$
like you wrote.
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up vote
2
down vote
In first $A'$ instead of $(-2x)$ you have $(-2-2x)$
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up vote
-1
down vote
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
So in fact, $$A'=left(-frac{1}{2}right)left(sqrt{1-2x-x^2}right)+ color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
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3 Answers
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3 Answers
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up vote
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You got A' wrong.
$ A = frac{3-x}{2}cdot(sqrt{1-2x-x^2}) = fcdot g$
where: $ f =frac{3-x}{2} $ , $ g = sqrt{1-2x-x^2} $
$A'= f'g + g'f$
$ f'g = (-frac{1}{2})(sqrt{1-2x-x^2})$ is correct, but the second part is $ g'f = (-2x -2)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$ rather than
$(-2x)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$
like you wrote.
add a comment |
up vote
0
down vote
accepted
You got A' wrong.
$ A = frac{3-x}{2}cdot(sqrt{1-2x-x^2}) = fcdot g$
where: $ f =frac{3-x}{2} $ , $ g = sqrt{1-2x-x^2} $
$A'= f'g + g'f$
$ f'g = (-frac{1}{2})(sqrt{1-2x-x^2})$ is correct, but the second part is $ g'f = (-2x -2)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$ rather than
$(-2x)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$
like you wrote.
add a comment |
up vote
0
down vote
accepted
up vote
0
down vote
accepted
You got A' wrong.
$ A = frac{3-x}{2}cdot(sqrt{1-2x-x^2}) = fcdot g$
where: $ f =frac{3-x}{2} $ , $ g = sqrt{1-2x-x^2} $
$A'= f'g + g'f$
$ f'g = (-frac{1}{2})(sqrt{1-2x-x^2})$ is correct, but the second part is $ g'f = (-2x -2)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$ rather than
$(-2x)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$
like you wrote.
You got A' wrong.
$ A = frac{3-x}{2}cdot(sqrt{1-2x-x^2}) = fcdot g$
where: $ f =frac{3-x}{2} $ , $ g = sqrt{1-2x-x^2} $
$A'= f'g + g'f$
$ f'g = (-frac{1}{2})(sqrt{1-2x-x^2})$ is correct, but the second part is $ g'f = (-2x -2)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$ rather than
$(-2x)(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$
like you wrote.
answered Nov 22 at 22:30
Daphna Keidar
1896
1896
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up vote
2
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In first $A'$ instead of $(-2x)$ you have $(-2-2x)$
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up vote
2
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In first $A'$ instead of $(-2x)$ you have $(-2-2x)$
add a comment |
up vote
2
down vote
up vote
2
down vote
In first $A'$ instead of $(-2x)$ you have $(-2-2x)$
In first $A'$ instead of $(-2x)$ you have $(-2-2x)$
answered Nov 22 at 22:25
asv
2661210
2661210
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up vote
-1
down vote
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
So in fact, $$A'=left(-frac{1}{2}right)left(sqrt{1-2x-x^2}right)+ color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
add a comment |
up vote
-1
down vote
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
So in fact, $$A'=left(-frac{1}{2}right)left(sqrt{1-2x-x^2}right)+ color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
add a comment |
up vote
-1
down vote
up vote
-1
down vote
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
So in fact, $$A'=left(-frac{1}{2}right)left(sqrt{1-2x-x^2}right)+ color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
So in fact, $$A'=left(-frac{1}{2}right)left(sqrt{1-2x-x^2}right)+ color{blue}{(-2 -2x)}left(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}}right)left(frac{3-x}{2}right)$$
edited Nov 22 at 22:47
answered Nov 22 at 22:28
amWhy
191k28223439
191k28223439
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In the first line of your derivation of A': after the first summand, your second summand should be $$color{blue}{(-2 -2x)}(frac{1}{2}cdot frac{1}{{sqrt{1-2x-x^2}}})(frac{3-x}{2})$$
– amWhy
Nov 22 at 22:24