Evaluate the indefinite integral: ∫ (e^x)sin(x) dx

Note: for what’s about to come, ' denotes derivative with respect to x. Method 1 (integration by parts): let I = (e^x)sin(x) dx let u = sin(x), u' = cos(x) and v' = e^x = v then integrate by parts, => I = uv - ∫u’v dx, substitute in u,v and u’ obtains: I =(e^x)sin(x) - ∫ (e^x)cos(x) dx () Now integrate by parts ∫ (e^x)cos(x) dx: let a = cos(x), a' = -sin(x) and b' = b = e^x hence: ∫ (e^x)cos(x) dx =(e^x)cos(x) + I, substitute into (): I = (e^x)(sin(x) + cos(x)) - I + C, for some constant C => I = 1/2(e^x)(sin(x) + cos(x)) + C  Method 2 (compare coefficients): Let y = (e^x)(Acos(x) + Bsin(x)), for some constants A, B to be determined => y' =(e^x)((A+B)cos(x) + (B-A)sin(x)) ≡(e^x)sin(x), hence by comparing coefficients, we have: B - A = 1 and A + B = 0 => B = 1/2, A = -1/2 => y = (1/2)(e^x)(sin(x) + cos(x)) + D, for some constants D

Answered by ShenZhen N. Maths tutor

11735 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

How can I recognise when to use a particular method for finding an integral?


How do I do this question: A small stone is projected vertically upwards from the point A with speed 11.2 m/s. Find the maximum height above A reached by the stone.


dh/dt = (6-h)/20. When t=0, h=1. Show that t=20ln(5/(6-h))


A curve (C) with equation y=3x^(0.5)-x^(1.5) cuts the X axis at point A and the origin, calculate the co-ordinates of point A.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences