x Turn on thread page Beta
 You are Here: Home >< Maths

# C4 Differentiation watch

1. What is

and why?

I know that

Thank you.
2. LaTex Error = Your computer is going to blow up.
3. (Original post by H3rrW4rum)
What is

and why?

I know that

Thank you.
Is the I meant to be a t ?
4. (Original post by wizz_kid)
Is the I meant to be a t ?
Nope.
5. Here's the actual question and my working so far:

Find the rate of change of I when t=3,

where I = 16 - 16(0.5)^t

My working so far:

When I differentiate the RHS wrt t I get ln 05.

But how do I differentiate the LHS wrt t?

Thanks.
6. You didn't ln the LHS correctly.
Any how, leave it as I = 16 - 16(0.5)^t and work out dI/dt.

a^t becomes (a^t)ln(a)
7. (Original post by vc94)
You didn't ln the LHS correctly.
Any how, leave it as I = 16 - 16(0.5)^t and work out dI/dt.

a^t becomes (a^t)ln(a)
Why can you not just

ln (1 - (I/16)) ?

And how can you differentiate 16 - 16(0.5)^t straight away?
8. (Original post by H3rrW4rum)
Here's the actual question and my working so far:

Find the rate of change of I when t=3,

where I = 16 - 16(0.5)^t

My working so far:

When I differentiate the RHS wrt t I get ln 05.

But how do I differentiate the LHS wrt t?

Thanks.
Implicit Differentiation.
9. I know if

So in this case

I just can't see how you get there.

EDIT: I can see it now, -16 is a constant you can just take out right? Then proceed as normal, put the -16 back in and you get the answer.
10. Correct, the -16 doesn't interfere!
11. (Original post by vc94)
Correct, the -16 doesn't interfere!
Yea I was looking at it for ages, knowing there was a much simpler way to do it (as is often the case) but just couldn't see it

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 8, 2011
Today on TSR

### Is uni even worth it?

Does anyone use their degree?

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams