This form pleases me

Calculus Level 4

π 4 π 4 x + π 4 2 cos ( 2 x ) d x \large \displaystyle \int_{\frac{-\pi}{4}}^{\frac{\pi}{4}} \dfrac{x+\frac{\pi}{4}}{2-\cos(2x)} \, dx

Find the largest integer that is less than or equals to the value of the integral above.

Try more Integral problems here .


The answer is 0.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

3 solutions

Dhruva Patil
Nov 21, 2014

Using basic Definite integral rules we get the answer π 2 6 3 \boxed{\frac{\pi ^{2}}{6\sqrt{3}}} =0.9497 And here lies the problem, the answer, going by the question should be 0. But the answer given here is 6 3 \left\lfloor 6\sqrt { 3 } \right\rfloor =10. @SandeepBhardwaj , you might want to change either the question or the answer.

Thanks. I have updated the answer to 0.

In future, if you spot any errors with a problem, you can “report” it by selecting the “dot dot dot” menu in the lower right corner. You will get a more timely response that way.

Calvin Lin Staff - 6 years, 6 months ago

What "basic definite integral rules" are you talking about?

Trevor Arashiro - 6 years ago

Could you please elaborate . How did you get your answer? My answer is π 2 24 3 \frac{\pi^2}{24\sqrt{3}} help @Calvin Lin

Rajdeep Dhingra - 6 years, 3 months ago

Log in to reply

U will get π/2 (π/3) (1/√3)

Ashwin Gopal - 6 years ago
Hassan Abdulla
Jun 1, 2018

π 4 π 4 x + π 4 2 cos ( 2 x ) d x = π 4 π 4 x 2 cos ( 2 x ) d x + π 4 π 4 π 4 1 2 cos ( 2 x ) d x / / π 4 π 4 x 2 cos ( 2 x ) d x = 0 odd function \begin{matrix} \int _{ \frac { -\pi }{ 4 } }^{ \frac { \pi }{ 4 } }{ \frac { x+\frac { \pi }{ 4 } }{ 2-\cos (2x) } dx } =\int _{ \frac { -\pi }{ 4 } }^{ \frac { \pi }{ 4 } }{ \frac { x }{ 2-\cos (2x) } dx } +\frac { \pi }{ 4 } \int _{ \frac { -\pi }{ 4 } }^{ \frac { \pi }{ 4 } }{ \frac { 1 }{ 2-\cos (2x) } dx } & & \color{#D61F06} // \int _{ \frac { -\pi }{ 4 } }^{ \frac { \pi }{ 4 } }{ \frac { x }{ 2-\cos (2x) } dx }=0 & & \color{#D61F06} \text{odd function} \end{matrix}

let I = π 4 π 4 π 4 1 2 cos ( 2 x ) d x = π 2 0 π 4 1 2 cos ( 2 x ) d x = π 4 0 π 2 1 2 cos ( u ) d u // u=2x \text{let I}=\frac { \pi }{ 4 } \int _{ \frac { -\pi }{ 4 } }^{ \frac { \pi }{ 4 } }{ \frac { 1 }{ 2-\cos (2x) } dx }=\frac { \pi }{ 2 } \int _{0}^{ \frac { \pi }{ 4 } }{ \frac { 1 }{ 2-\cos (2x) } dx }=\frac { \pi }{ 4 } \int _{0}^{ \frac { \pi }{ 2 } }{ \frac { 1 }{ 2-\cos (u) } du } \color{#D61F06}{\text{ // u=2x}}

let t = t a n ( x 2 ) tan(\frac{x}{2}) Weierstrass Substitution

I = π 4 0 1 1 2 ( 1 t 2 1 + t 2 ) ( 2 d t 1 + t 2 ) = π 2 0 1 d t 3 t 2 + 1 = π 2 3 0 1 3 d t ( 3 t ) 2 + 1 = π 2 3 tan 1 ( 3 t ) 0 1 = π 2 6 3 I=\frac { \pi }{ 4 } \int _{0}^{1}{ \frac { 1 }{ 2-\left(\frac{1-t^2}{1+t^2}\right ) } \left (\frac{2dt}{1+t^2}\right ) }=\frac {\pi}{2} \int _{0}^{1} {\frac { dt }{ 3t^2+1}}=\frac {\pi}{2\sqrt{3}} \int _{0}^{1} {\frac { \sqrt{3} dt }{ \left (\sqrt{3}t \right )^2+1}}=\frac {\pi}{2\sqrt{3}}\left . \tan^{-1}(\sqrt{3}t) \right |_{0}^1=\frac {\pi^2}{6\sqrt{3}}

Ayush Kumawat
Jul 31, 2015

1st we use king. Then basic techniques of indefinite integration. Its comes out to be. .94

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...