Eric Nicholas K's answer to Sonia's Secondary 4 A Maths Singapore question.

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Eric Nicholas K
Eric Nicholas K's answer
5997 answers (Tutor Details)
1st
Hi Sonia!

I'm very sorry for the extremely messy handwriting.

We need to invoke the quotient rule in this case since you have an expression which is some numerator divided by denominator. The formula goes like this:

"(keep den, diff num - keep num, diff den) / (den^2)"

Now, we are differentiating (cos 2x)^2 instead of x^2, so the "chain" is cos 2x, which we must differentiate as well.

The chain is cos 2x, so we are differentiating cos 2x instead of the usual cos x, so '2x' is a "second chain", which we must also differentiate.

The rest is messy simplification. I'm sorry!