Help with physics/maths

Yami Silver

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Hello NB, I'm studying A level Further Maths and I'm currently doing the applied unit M2 (M standing for mechanics).
So, I have a simple question: How would one integrate/differentiate ae^(kt)? I missed the lesson on that and I won't be able to see my teacher till Tuesday and I'm practicing past exam papers.
Thank you :D
 

Amir el genio

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∫e^(-kt) dt = ∫(e^u)(-du/k) = ∫(e^u)(-1/k)du
= (-1/k)∫e^u du [since k is a constant, we can pull that factor outside the integral]
= (-1/k)e^u + C [the integral of e^x dx is e^x]

Now reverse the earlier substitution:
= (-1/k)e^(-kt)+C

Which can also be written as:
-1/[ke^(kt)] + C
 
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