Final answer:
To solve the initial value problem y'' + y' = sec(t), with initial conditions y(0) = 6 and y'(0) = 3, use the method of variation of parameters. The solution is y(t) = 2 + 4cos(t) + 4sin(t) - tcos(t) + sin(t) * ln(cos(t)).
Step-by-step explanation:
The given initial value problem is y'' + y' = sec(t), with the initial conditions y(0) = 6 and y'(0) = 3. To solve this, we can use the method of variation of parameters. Let's assume the solution is of the form y(t) = u(t)cos(t) + v(t)sin(t), where u(t) and v(t) are unknown functions. Substituting this into the differential equation, we can solve for u'(t) and v'(t). After finding u(t) and v(t), we can substitute these back into the assumed solution to get the final answer.
In this case, the solution to the initial value problem is y(t) = 2 + 4cos(t) + 4sin(t) - tcos(t) + sin(t) * ln(cos(t)).