Evaluate the following integral: f(t)=(1)/(pi) int_0^(pi) cos(t sin theta)d theta

Frances Pham

Frances Pham

Answered question

2022-11-19

Evaluate the following integral:
f ( t ) = 1 π 0 π cos ( t sin θ ) d θ
I started with the 'standard' form of the Laplace Transform:
L ( cos ω t ) = s s 2 + ω 2
Now I can substitute to obtain:
L [ f ( t ) ] = 1 π 0 π s s 2 + sin 2 θ d θ
But how do I get back? Taking the 's' out:
L [ f ( t ) ] = s π 0 π d θ s 2 + sin 2 θ
But how to proceed now?

Answer & Explanation

avuglantsaew

avuglantsaew

Beginner2022-11-20Added 15 answers

If you divide by cos 2 θ in numerator and denominator, then,
L [ f ( t ) ] = s π 0 π sec 2 θ d θ sec 2 θ s 2 + tan 2 θ
L [ f ( t ) ] = s π 0 π sec 2 θ s 2 + ( 1 + s 2 ) tan 2 θ d θ
Since, d ( tan θ ) = sec 2 θ, the further part is easy to solve.
Edited for query in comment:
L [ f ( t ) ] = s π 0 π sec 2 θ s 2 + ( 1 + s 2 ) tan 2 θ d θ
which can be transformed to the form
1 a 2 + x 2 d x = 1 a tan 1 x a + c
by substituting x = tan θ

Do you have a similar question?

Recalculate according to your conditions!

New Questions in Differential Equations

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?