(a) Find the differential dy.
y = cos(x)
To find dy we take derivative of y
y = cosx
So [tex]\frac{dy}{dx}=-sin(x)[/tex]
Multiply by dx on both sides
dy = -sin(x) dx
(b) x = π/3, dx = 0.1
Plug in the values and find out dy
dy = -sin(\frac{\pi}{3}) * 0.1
dy = -0.0866
dy= -0.087
