How to test a function for condition and stabilty?

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How can I test the condition and stability of the following function, for values $x=0$, $x=0.25$ and $x=10^-5$?
$$
f(x) = frac1-cos(2x)x
$$
What should one do here? For condition, I think I should do the following:
$$
K = left|fracf'(x)f(x) cdot xright|
$$
and check if it's $>> 1$ or $< 10$.



1) Am I right for the condition? And how to check for that $x$ values given above? If not, how would be the right way?



2) How to check the stability also for that values?



Thank you in advance!!







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  • You could say $cos 2x = 1-2sin^2 x$ and then $f(x) = frac 2sin^2 xx$ and you might have some experience already with the function $frac sin xx$
    – Doug M
    Jul 19 at 21:34










  • because of the undefined form 0/0 you mean?
    – ZelelB
    Jul 19 at 21:44










  • Your function is undefined at $0.$ However, the limit exists.
    – Doug M
    Jul 19 at 21:45










  • yep, but how to answer the questions above? What should I do in the exam for this problem?
    – ZelelB
    Jul 19 at 21:45










  • would be greateful for any help! I have my last exam tomorrow, and this comes every time :/
    – ZelelB
    Jul 19 at 22:19














up vote
0
down vote

favorite












How can I test the condition and stability of the following function, for values $x=0$, $x=0.25$ and $x=10^-5$?
$$
f(x) = frac1-cos(2x)x
$$
What should one do here? For condition, I think I should do the following:
$$
K = left|fracf'(x)f(x) cdot xright|
$$
and check if it's $>> 1$ or $< 10$.



1) Am I right for the condition? And how to check for that $x$ values given above? If not, how would be the right way?



2) How to check the stability also for that values?



Thank you in advance!!







share|cite|improve this question





















  • You could say $cos 2x = 1-2sin^2 x$ and then $f(x) = frac 2sin^2 xx$ and you might have some experience already with the function $frac sin xx$
    – Doug M
    Jul 19 at 21:34










  • because of the undefined form 0/0 you mean?
    – ZelelB
    Jul 19 at 21:44










  • Your function is undefined at $0.$ However, the limit exists.
    – Doug M
    Jul 19 at 21:45










  • yep, but how to answer the questions above? What should I do in the exam for this problem?
    – ZelelB
    Jul 19 at 21:45










  • would be greateful for any help! I have my last exam tomorrow, and this comes every time :/
    – ZelelB
    Jul 19 at 22:19












up vote
0
down vote

favorite









up vote
0
down vote

favorite











How can I test the condition and stability of the following function, for values $x=0$, $x=0.25$ and $x=10^-5$?
$$
f(x) = frac1-cos(2x)x
$$
What should one do here? For condition, I think I should do the following:
$$
K = left|fracf'(x)f(x) cdot xright|
$$
and check if it's $>> 1$ or $< 10$.



1) Am I right for the condition? And how to check for that $x$ values given above? If not, how would be the right way?



2) How to check the stability also for that values?



Thank you in advance!!







share|cite|improve this question













How can I test the condition and stability of the following function, for values $x=0$, $x=0.25$ and $x=10^-5$?
$$
f(x) = frac1-cos(2x)x
$$
What should one do here? For condition, I think I should do the following:
$$
K = left|fracf'(x)f(x) cdot xright|
$$
and check if it's $>> 1$ or $< 10$.



1) Am I right for the condition? And how to check for that $x$ values given above? If not, how would be the right way?



2) How to check the stability also for that values?



Thank you in advance!!









share|cite|improve this question












share|cite|improve this question




share|cite|improve this question








edited Jul 19 at 23:02









Somos

11.6k1933




11.6k1933









asked Jul 19 at 21:14









ZelelB

1256




1256











  • You could say $cos 2x = 1-2sin^2 x$ and then $f(x) = frac 2sin^2 xx$ and you might have some experience already with the function $frac sin xx$
    – Doug M
    Jul 19 at 21:34










  • because of the undefined form 0/0 you mean?
    – ZelelB
    Jul 19 at 21:44










  • Your function is undefined at $0.$ However, the limit exists.
    – Doug M
    Jul 19 at 21:45










  • yep, but how to answer the questions above? What should I do in the exam for this problem?
    – ZelelB
    Jul 19 at 21:45










  • would be greateful for any help! I have my last exam tomorrow, and this comes every time :/
    – ZelelB
    Jul 19 at 22:19
















  • You could say $cos 2x = 1-2sin^2 x$ and then $f(x) = frac 2sin^2 xx$ and you might have some experience already with the function $frac sin xx$
    – Doug M
    Jul 19 at 21:34










  • because of the undefined form 0/0 you mean?
    – ZelelB
    Jul 19 at 21:44










  • Your function is undefined at $0.$ However, the limit exists.
    – Doug M
    Jul 19 at 21:45










  • yep, but how to answer the questions above? What should I do in the exam for this problem?
    – ZelelB
    Jul 19 at 21:45










  • would be greateful for any help! I have my last exam tomorrow, and this comes every time :/
    – ZelelB
    Jul 19 at 22:19















You could say $cos 2x = 1-2sin^2 x$ and then $f(x) = frac 2sin^2 xx$ and you might have some experience already with the function $frac sin xx$
– Doug M
Jul 19 at 21:34




You could say $cos 2x = 1-2sin^2 x$ and then $f(x) = frac 2sin^2 xx$ and you might have some experience already with the function $frac sin xx$
– Doug M
Jul 19 at 21:34












because of the undefined form 0/0 you mean?
– ZelelB
Jul 19 at 21:44




because of the undefined form 0/0 you mean?
– ZelelB
Jul 19 at 21:44












Your function is undefined at $0.$ However, the limit exists.
– Doug M
Jul 19 at 21:45




Your function is undefined at $0.$ However, the limit exists.
– Doug M
Jul 19 at 21:45












yep, but how to answer the questions above? What should I do in the exam for this problem?
– ZelelB
Jul 19 at 21:45




yep, but how to answer the questions above? What should I do in the exam for this problem?
– ZelelB
Jul 19 at 21:45












would be greateful for any help! I have my last exam tomorrow, and this comes every time :/
– ZelelB
Jul 19 at 22:19




would be greateful for any help! I have my last exam tomorrow, and this comes every time :/
– ZelelB
Jul 19 at 22:19















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