Unit 3 of 6 · Techniques of differentiation
Differentiate standard functions
Retain inner factors, radian assumptions and logarithm domains.
Trigonometric derivatives use radians
Identify the inner function before choosing a derivative. Use radian input, keep the inner derivative as a factor, then check where the original function is defined.
For a differentiable inner function u, all six source rows are:
Function:
- Derivative with respect to x:
Function:
- Derivative with respect to x:
Function:
- Derivative with respect to x:
Function:
- Derivative with respect to x:
Function:
- Derivative with respect to x:
Function:
- Derivative with respect to x:
Setting u=x gives the source’s basic column.
The source spells csc as cosec and shades the basic secant/cosecant rows as listed in MF27.
Preserve the relevant nonzero sine/cosine denominators.
Degrees would introduce an additional angle-conversion factor; these displayed formulas assume radians.
Exponentials and logarithms
The four source rows, including their general inner-function forms, are:
Function:
- Derivative with respect to x:
Function:
- Derivative with respect to x:
Function:
- Derivative with respect to x:
Function:
- Derivative with respect to x:
The exponential base is positive.
A real logarithm additionally needs u>0 and base a>0, a≠1.
Setting u=x gives every printed basic formula.
Simplifying an answer does not change its original domain: for example, the identity used in Example 7(b) is valid only where its tangent/secant expression exists.
Try these examples
Open an example in chapter practice. Try it first, then read its solution. Use “Learn this step” to return to this unit.
- Choose useful trig identities before differentiating
- Prove a cotangent derivative and distinguish a reciprocal from an inverse
- Prove a squared-cosine derivative identity
- Differentiate exponentials and logarithms with their inner factors
- Simplify a logarithm before differentiating
- Practise products, exponentials and a logarithmic square root
- Use first principles and the sine small-angle limit
- Derive the exponential derivative using its limiting quotient