Finding interval where second order ODE has unique solution

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SUMMARY

The discussion focuses on applying the existence and uniqueness theorem to the second order ordinary differential equation (ODE) $$y''+\tan(x)y=e^x$$ with initial conditions $$y(0)=1$$ and $$y'(0)=0$$. The user reformulates the ODE as $$\cos x\ y^{\ ''} + \sin x\ y = e^{x}\ \cos x$$ and identifies $$a_{2}(x) = \cos x$$, confirming that $$a_{2}(0) = 1 \ne 0$$. This verification establishes that a unique solution exists on an interval where $$\cos x$$ remains non-zero.

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find_the_fun
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I'm a little stuck getting started on this question. $$y''+\tan(x)y=e^x$$ with $$y(0)=1,y'(0)=0$$. I know the existence and uniqueness theorem
Let $$a_n(x),a_{n-1}(x),...,a_0(x)$$ and g(x) be continuous on an Interval I and let $$a_n(x)$$ not be 0 for every x in this interval. If x=x_0 is any point in this interval, then a solution Y(x) of the initial value problem exists on the interval and is unique.
for an nth order initial value problem

How do I apply the theorem?
 
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find_the_fun said:
I'm a little stuck getting started on this question. $$y''+\tan(x)y=e^x$$ with $$y(0)=1,y'(0)=0$$. I know the existence and uniqueness theorem
for an nth order initial value problem

How do I apply the theorem?

Let's write the second order linear ODE as...

$\displaystyle \cos x\ y^{\ ''} + \sin x\ y = e^{x}\ \cos x, \ y(0)=1,\ y^{\ '} (0)=0\ (1)$

Here $a_{2}(x) = \cos x$, and is $a_{2} (0) = 1 \ne 0$, so that the existence and uniqueness theorem is verified...

Kind regards

$\chi$ $\sigma$
 

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