To find dy/dx of y = x cos x, we can use the product rule of differentiation, which states that the derivative of a product of two functions is equal to the first function times the derivative of the second function plus the second function times the derivative of the first function.
In this case, we have:
y = x cos x
Using the product rule, we get:
dy/dx = cos x - x sin x
Therefore, the correct option is: cos x - x sin x.
To explain it in simple terms, the derivative of x cos x is equal to cos x minus x times the derivative of cos x, which is -sin x. This gives us cos x - x sin x as the answer.