Note:- If y = cos(ax) ; then dy/dx = -a*sin(ax)

Now,

`y = 5cos(9x + 1)`

`dy/dx = y' = -5*(sin(9x+1))*9`

`or, dy/dx = y' = -45sin(9x+1)`

``

Note:- If y = cos(ax) ; then dy/dx = -a*sin(ax)

Now,

`y = 5cos(9x + 1)`

`dy/dx = y' = -5*(sin(9x+1))*9`

`or, dy/dx = y' = -45sin(9x+1)`

``