Fourier series approximation of tan(θ) on [-π/2, π/2]

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
3 replies · 2K views
mundane
Messages
56
Reaction score
0
I am SO annoyed with this problem. Ready to jump out a window.

Homework Statement



Find the first three terms of the Fourier series that approximates f(θ) = tan(θ) from θ = -π/2 to π/2.

The Attempt at a Solution



So, I know that for an equation on [[itex]\frac{-b}{2}[/itex], [itex]\frac{b}{2}[/itex]], to define the Fourier series for that equation we use f(x)={a0+a1cosx+a2cos2x+ ... +b1sinx+b2sin2x+ ...}

I only need to find the first three terms, so its just a0+a1cosx+b1sinx.

a0 is defined as [itex]\frac{1}{\pi}[/itex][itex]\intf(x)dx[/itex] definite integral from -π/2 to π/2.

a1 is defined as [itex]\frac{2}{\pi}[/itex][itex]\int\f(x)cos(2πx/π)dx[/itex] definite integral from -π/2 to π/2.

b1 is defined as [itex]\frac{2}{\pi}[/itex][itex]\int\f(x)sin(2πx/π)dx[/itex] definite integral from -π/2 to π/2.For a0, my antiderivative was -log(cos(x)). After substitution, a0=0.

For a1, my antiderivative was log(cos(x))-(1/2)cos(2x). After substitution, a1=0.

I have not done b1 yet. Am I being trolled?

Does this ave something to do with the fact that tan(x) is undefined at those two interval points? Am I going in the wrong direction?
 
Physics news on Phys.org
If a function is odd, can it have cosine terms?
If a function is even, can it have sine terms?
 
Sorry, I didn't mean to repost. I was trying to change the red font and it reposted. Sorry.