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Suppose you know that f(x)=sec(x) and W(f,g)=sec(x), also. Find g(x).

User Janely
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Final answer:

To find g(x), given that f(x)=sec(x) and the Wronskian W(f,g)=sec(x), we solve the first-order linear differential equation that results from the information provided. This involves using an integrating factor and integrating both sides of the equation.

Step-by-step explanation:

The student has provided the following information: the function f(x) = sec(x), and the Wronskian of f and g, W(f,g) = sec(x), is also given.

The Wronskian is a determinant used in the analysis of differential equations and is defined for two functions f(x) and g(x) as:

W(f,g) = f(x)g'(x) - f'(x)g(x).

Given that f(x) = sec(x), we can calculate f'(x):

f'(x) = sec(x)tan(x).

Now, we substitute f(x) and f'(x) into the Wronskian definition:

W(f,g) = sec(x)g'(x) - sec(x)tan(x)g(x).

We know W(f,g) = sec(x), hence:

sec(x)g'(x) - sec(x)tan(x)g(x) = sec(x).

To find g(x), we solve this first-order linear differential equation. Dividing through by sec(x), we get:

g'(x) - tan(x)g(x) = 1.

This can be solved using an integrating factor, which in this case is e-&#积; tan(x)dx = e-ln|sec(x)| = |cos(x)|.

By multiplying both sides of the equation with the integrating factor, we can find g(x) through integration.

User Brandon Kreisel
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