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# differentiating sinxcos(-y) watch

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1. Hi

I'm working on the implicit question sinxcos(-y)=tanxy which I have to get dy/dx from. I've just managed to differentiate tanxy, and I have nearly done the first bit, differentiating sinxcos(-y) but do I leave it in this form or do I simplify further?

sinxcos(-y)= -cosxcos(-y)/sinxsin(-y)
2. (Original post by hamzramz)
Hi

I'm working on the implicit question sinxcos(-y)=tanxy which I have to get dy/dx from. I've just managed to differentiate tanxy, and I have nearly done the first bit, differentiating sinxcos(-y) but do I leave it in this form or do I simplify further?

sinxcos(-y)= -cosxcos(-y)/sinxsin(-y)
cos(-y)=cosy
cos is an even function
3. (Original post by hamzramz)
Hi

I'm working on the implicit question sinxcos(-y)=tanxy which I have to get dy/dx from. I've just managed to differentiate tanxy, and I have nearly done the first bit, differentiating sinxcos(-y) but do I leave it in this form or do I simplify further?

sinxcos(-y)= -cosxcos(-y)/sinxsin(-y)
So the equation is sin x cos y = tan xy
Differentiate sin x cos y using the product rule.
Differentiate tan xy using the chain rule.
Collect like terms.

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