It should be sqrt 65.

Anyway, outside the sin inverse there must be a multiplier 1/sqrt65 as part of the “reverse chain”.

sorry, just to ask what is the reverse chain about? i never heard it before haha, i solved the qn based on my formula list....

also, is it possible to help take a look at the question i posted recently? i tried solving part a and got the answer wrong, i constantly got 1.84 (radian mode) after multiple tries and the ans key was 4.69

tried degree mode too but i got 4 instead of 4.69

Sorry, my mistake. I made a mistake with the format. I mixed it up with the arctan version [arctan means tan inverse]. There is no multiplier for arcsin [arcsin means sin inverse].

Your answer is correct.

The arctan version has a multiplier outside. Had it become arctan, the multiplier 1 / sqrt 65 is needed.

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Also, a second mistake of mine. The chain rule part doesn't apply here because your term in the bracket, x + 4, differentiates into 1 (so technically reversing the chain means dividing by 1).

However, if the term inside the bracket is like 2x + 3, things will be different.