derivative of y=cos(7x) — step-by-step solution

We save the definition:

y = \cos (7 x)

Let's differentiate:

\frac{d}{d x} (\cos (7 x))

Apply the differentiation rule:

\frac{d}{d x} (\cos (f)) = - \frac{d}{d x} (f) \cdot \sin (f)

with f =

7 x

ⓘ The derivative of cos(x) is -sin(x):

\frac{d}{d x} (\cos (7 x))

- \frac{d}{d x} (7 x) \cdot \sin (7 x)

- \frac{d}{d x} (7 x) \cdot \sin (7 x)

ⓘ A constant factor stays in front of the derivative, (k*u)' = k*u':

\frac{d}{d x} (7 x)

7

▶Derivative:

- 7 \cdot \sin (7 x)