Differentiating (x+siny): i don't get why we differentiate siny as cosy.(dy/dx). isn't it constant and its derivative is equal to 0? so why is the answer 1+cosy.(dy/dx) instead of just 1?

Question

accessdenied · Answer

It would only be constant if you were taking the partial derivative with respect to x or the problem specifies that y is constant / does not change with respect to x.

phi · Answer

if y were known to be constant you are correct. But (as you know) it is common practice to label variables as x,y,z etc.

anonymous · Answer

ok i got it. thanks