A-level Maths revision · Pure, year 2

Integrating exponentials and trig

The idea

Reverse the standard derivatives: ∫ekx dx=1kekx+c\int e^{kx}\,dx = \frac{1}{k}e^{kx} + c, ∫1x dx=ln⁡∣x∣+c\int \frac{1}{x}\,dx = \ln|x| + c, ∫cos⁡kx dx=1ksin⁡kx+c\int \cos kx\,dx = \frac{1}{k}\sin kx + c, ∫sin⁡kx dx=−1kcos⁡kx+c\int \sin kx\,dx = -\frac{1}{k}\cos kx + c and ∫sec⁡2kx dx=1ktan⁡kx+c\int \sec^2 kx\,dx = \frac{1}{k}\tan kx + c.

  1. Match each term to a standard result.
  2. Divide by the coefficient of xx inside.
  3. Add +c+ c, or apply the limits for a definite integral.

Watch out Integrating e2xe^{2x} gives 12e2x\frac{1}{2}e^{2x}: divide by 22, do not multiply.

See it worked

Worked example

Find ∫(e3x+cos⁡2x) dx\int (e^{3x} + \cos 2x)\,dx.

  1. ∫e3x dx=13e3x\int e^{3x}\,dx = \frac{1}{3}e^{3x}.
  2. ∫cos⁡2x dx=12sin⁡2x\int \cos 2x\,dx = \frac{1}{2}\sin 2x.
  3. 13e3x+12sin⁡2x+c\frac{1}{3}e^{3x} + \frac{1}{2}\sin 2x + c.

Answer 13e3x+12sin⁡2x+c\frac{1}{3}e^{3x} + \frac{1}{2}\sin 2x + c

Your turn

Question 1Non-calculator3 marks

Find ∫(e2x+4x)dx\int \left(e^{2x} + \frac{4}{x}\right)dx, for x>0x > 0.

Question 2Non-calculator3 marks

Find ∫sin⁡3x dx\int \sin 3x\,dx.

Question 3Non-calculator3 marks

Find the exact value of ∫016e2x dx\int_0^1 6e^{2x}\,dx.

In past papers

13 official questions in 13 papers since 2018. The latest:

All A-level Maths past papers

A-level Maths Pro, Pearson Edexcel 9MA0

A-level Maths Pro

£129 once

Price rises to £199 on 1 January. Save £70 by joining before then.

At least 12 months of access

By paying you agree to our Terms and get access straight away, which ends your 14-day cancellation right.

No VAT is charged.