ATAR Notes: Forum

VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: iVincent on July 05, 2015, 05:44:29 pm

Title: How do you antidifferentiate this equation?
Post by: iVincent on July 05, 2015, 05:44:29 pm
Can anyone show me how to antiderive this equation? This question is taken from the VCAA exam Methods (CAS) Exam 1 2012, Q9b.
Title: Re: How do you antidifferentiate this equation?
Post by: brightsky on July 05, 2015, 05:51:13 pm
Integration by parts.

int x cosx dx
= int d/dx (sinx) x dx
= x sinx - int sinx d/dx (x) dx
= x sinx - int sinx dx
= x sinx + cosx + c

Title: Re: How do you antidifferentiate this equation?
Post by: Floatzel98 on July 05, 2015, 06:21:12 pm
Just a bit confused, i thought integration by parts was not in the Methods SD, let alone Specialist. How would we know how to answer that, especially if it's on Exam 1 (Non-Calc)?
Title: Re: How do you antidifferentiate this equation?
Post by: keltingmeith on July 05, 2015, 06:25:28 pm
Just a bit confused, i thought integration by parts was not in the Methods SD, let alone Specialist. How would we know how to answer that, especially if it's on Exam 1 (Non-Calc)?

This is the exam in question. As you can see, the first part of this was a set-up so that you knew how to do it. They even say in the first part of the question to use your result from part a (in bold, even)
Title: Re: How do you antidifferentiate this equation?
Post by: Floatzel98 on July 05, 2015, 06:30:54 pm
This is the exam in question. As you can see, the first part of this was a set-up so that you knew how to do it. They even say in the first part of the question to use your result from part a (in bold, even)
Ah okay. That makes a lot more sense. That makes it an integration by recognition question then, yes?
Title: Re: How do you antidifferentiate this equation?
Post by: pi on July 05, 2015, 06:31:48 pm
Ah okay. That makes a lot more sense. That makes it an integration by recognition question then, yes?

Do the question and find out ;)
Title: Re: How do you antidifferentiate this equation?
Post by: Floatzel98 on July 05, 2015, 06:39:36 pm
It might out be set out the best, but is the working okay, (if you can actually see it)? I checked the examiners report and the answers is the same :)
Title: Re: How do you antidifferentiate this equation?
Post by: keltingmeith on July 05, 2015, 06:46:51 pm
It might out be set out the best, but is the working okay, (if you can actually see it)? I checked the examiners report and the answers is the same :)

When you've jumped to calculation of the definite integral, as long as you also write the actual definite integral, that working should be perfect.