Hello student,

As per your query the derivative of (cosx)  is (-sinx)  .

it is often People remembers in their memory but you should know how to show it. to find the derivative of cos x,We know that cos x is =1/sec x so if you find the derivative of 1 /sec x .you will have the derivative of cosx. You just have to use the quotient rule for the derivative to find the derivative . hope this will help you

Hello,

The derivative of cosx is -sin(x) . The procedure to do this is :

let f(x)=cosx

f ' (x) = lim(h->0) ( f(x+h) - f(x) ) / h

= lim(h->0) (cos(x+h) - cosx )/h

= lim(h->0) ( -2 (sin(x + h/2))sin(h/2) )/h

= lim(h->0) -1 * sin(x+h/2)    (as h=0)

= -sinx