Solution to this differential equation that does not diverge at x=0. \tan x \; \frac{\t

Alejandro Atkins

Alejandro Atkins

Answered question

2022-04-20

Solution to this differential equation that does not diverge at x=0.
tanx dydx+y=extanx
By using the integrating factor μ(x)=cosx, I solved it as an equation in full differentials and got the solution
y(x)=Acscx+12ex(1cotx)
However, the question I am solving asks for a solution that does not diverge at x=0, which this solution clearly does because of the cotx. How can I get a solution that converges?

Answer & Explanation

Jonas Dickerson

Jonas Dickerson

Beginner2022-04-21Added 22 answers

Step 1
Notice that
Acsc(x)+12ex(1-cot(x))=Asin(x)+ex2(sin(x)-cos(x)sin(x))
=A+ex(sin(x)-cos(x))2sin(x).
Step 2
Notice that the divergence at 0 occurs because sin(0)=0. Consider the numerator,
A+ex(sin(x)-cos(x))2.
At 0, this numerator is equal to A12. This leaves you with the only option A=12, to ensure the singularity at 0 becomes removable.

Rey Mcmillan

Rey Mcmillan

Beginner2022-04-22Added 11 answers

At x=0, we want A csc x=12excotx. By representing csc x and cot x in their complex exponential form, and substituting x=0, we get A=12.

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