[attachmentid=4182754]

As for the first part,
Firstly, you should know the formula to calculate the concentration of OH- ions.
Secondly, the concentration of aqueous ammonia varies with volume so you should take note of that.

But for second part..... I am not sure.

RED-HAIR-SHANKS Critical_Fallacy Can you please check for me whether my answer is correct or not. 

[attachmentid=4182754]

As for the first part,
Firstly, you should know the formula to calculate the concentration of OH- ions.
Secondly, the concentration of aqueous ammonia varies with volume so you should take note of that.

But for second part..... I am not sure.

RED-HAIR-SHANKS Critical_Fallacy Can you please check for me whether my answer is correct or not. 

I've stuck in this question before. Here, let me give you a hint that will kick-start your momentum in solving this question:

Multiply both the LHS and RHS of the equation by .

I think I know why you're having a trouble with this question because I was having the same problem too. There are possibly many ways for you to solve it, either by multiplying the into the parentheses, or by using product rule. But, I've done it using both said methods and I still couldn't prove the equation albeit going through a lot of steps. The thing here is that you have to know which is the simplest method that you can execute in order to arrive at the correct solution. chocobo7779 taught me this, and it's called Occam's Razor.

Find the volume.

When's the due date?

So I guess it's done by now?

Is the substitution is t= tan (x/2)
And the answer is 1/4 tan (x/2) + 1/12 tan ^3 (x/2) + c ?

Here's the 3rd term trial exam paper from my school
https://www.dropbox.com/s/99hdvx3vxirr0i8/maths%20t.pdf?dl=0
-Maths T

https://www.dropbox.com/s/gf7k0m9wd6iiq6z/ps.pdf?dl=0
-PA