integration help (MX2) (3 Viewers)

[umm what]

is that right???

 

[deswa1]

Yep, that's right. BTW, your writing is amazing

 

[umm what]

Thanks mate
I will post up some more questions, could you check em for me please ?

Yep, that's right. BTW, your writing is amazing

 

[barbernator]

for efficiency and simplicity, i would use ln(x) instead of loge(x), but each to their own

 

[deswa1]

To check if you are right, go to http://www.wolframalpha.com

 

[umm what]

whats the integration of sin^3 x * cos^3 X ??

 

[umm what]

Is this right?

whats the integration of sin^3 x * cos^3 X ??

 

[barbernator]

change one of the cos^2 x to 1-sin^2x, and let u=sinx

 

[umm what]

i did....dunno how to work it outt

change one of the cos^2 x to 1-sin^2x, and let u=sinx

 

[deswa1]

View attachment 24971
Is this right?

Nope, that's wrong. For future, just check your answers on the website I posted. For a question like yours, type in something like "integrate from 0 to ln2 (x)e^(-x)

 

[AAEldar]

View attachment 24971
Is this right?

You have to put the bounds around the first part as well - the whole answer should be numerical instead of algebraic.

 

[barbernator]

i did....dunno how to work it outt

u will have a simple substitution, du=cosxdx. which will leave the integral of u^3-u^5.

for your other integral, make sure you evaluate the unintegrated term from 0 to ln2 as well

 

[umm what]

right???
coz Wolfram gives a completely different answer in cos x

u will have a simple substitution, du=cosxdx. which will leave the integral of u^3-u^5.

for your other integral, make sure you evaluate the unintegrated term from 0 to ln2 as well

 

[umm what]

http://integrals.wolfram.com/index.jsp?expr=sin^3+x+*+cos^3+x&random=false

 

[Siddy123]

wow, nice handwriting!!!!!!!!

 

[barbernator]

http://integrals.wolfram.com/index.jsp?expr=sin^3+x+*+cos^3+x&random=false

same shit different smell, test the derivative of your answer to see if its correct

 

[deswa1]

Yeah, your answer is right. If you end up getting a different answer from wolfram, you can ask it to differenriate your answer and then if you get the original question, obviously you are right.

 

[Carrotsticks]

You do indeed have very nice handwriting.

A tip:

Try to avoid the U substitution for simple questions like this. You could have actually done it all in one go (ie: From question to answer in 1 line) by recognising that you need to split it, then having a log and an inverse tan for the integral, then fixing up the constants (which is just half).

 

[deswa1]

You do indeed have very nice handwriting.

A tip:

Try to avoid the U substitution for simple questions like this. You could have actually done it all in one go (ie: From question to answer in 1 line) by recognising that you need to split it, then having a log and an inverse tan for the integral, then fixing up the constants (which is just half).

About this, in a test, how many lines would you recommend doing it in. Do you think markers wouldn't like it in just one line or is that fine?

 

[umm what]

I used to do this way....but i saw they make a U substitution in past papers

You do indeed have very nice handwriting.

A tip:

Try to avoid the U substitution for simple questions like this. You could have actually done it all in one go (ie: From question to answer in 1 line) by recognising that you need to split it, then having a log and an inverse tan for the integral, then fixing up the constants (which is just half).