I have to find the form of the function h ( t ) in this equation: h &

mravinjakag

mravinjakag

Answered question

2022-06-15

I have to find the form of the function h ( t ) in this equation:
h ( t ) θ h ( t ) 2 + 1 = 0
with h ( T ) = C where T and C are constants and T 0
At first I thought it was a Bernoulli differential equation and I tried:
V ( t ) = 1 h ( t ) V ( t ) = h ( t ) h ( t ) 2
My equation becomes worse:
V ( t ) θ 2 + 1 V ( t ) 2 = 0
Then I tried with the integrating factor:
( e t h ( t ) ) = 2 e t h ( t ) e t
e t h ( t ) = 2 e t h ( t ) e t
I'm stuck here because h ( t ) is not a variable, is a function and I have to find how it looks like.
Edit: I forgot: θ is a constant.
How can I solve this problem?

Answer & Explanation

Korotnokby

Korotnokby

Beginner2022-06-16Added 19 answers

Try
h ( t ) = c e θ 2 t + 2 θ .
Then
h ( t ) θ 2 h ( t ) + 1 = c θ 2 e t θ 2 c θ 2 e t θ 2 1 + 1 = 0.
Furthermore, h ( T ) = C. That is,
c e θ 2 T + 2 θ = C .
From where
c = ( C 2 θ ) e θ 2 T .
veirarer

veirarer

Beginner2022-06-17Added 9 answers

It is almost a linear equation, it has a free term. The idea is to use the variation of parameters. Write
h ( t ) = c e θ 2 t
where c is not a constant, but a new function. You get an equation for c that is rather simple.

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