Here is the question:
I have posted a link there to this topic so the OP can see my work.Differential Equations HW HELP!?
13. y'' + y = sec(t), 0< t < π/2; y = (cos t) ln cos t + t sin t
In each of Problems 7 through 14, verify that each given function is a solution of the differential equation.
I'm currently trying to review derivatives, but trig derivatives are super hard. Help?