Verify that y(t) = Acos(ωt − φ) is a solution to the differential equation (1.1.7), wher...

Verify that y(t) = Acos(ωt − φ) is a solution to the differential equation (1.1.7), where A,ω, and φ are constants with A and ω nonzero. Determine the constants A and φ (with |φ| < π radians) in the particular case when the initial conditions are