Using Euler's Formula exp(i)=cos()+isin() show that (t)=2acos(t)-2bsin(t) can also be expressed as (t)= cos(t-)

Using Euler's Formula exp(iφ)=cos(φ)+i•sin(φ) show that θ(t)=2a•cos(ωt)-2b•sin(ωt) can also be expressed as θ(t)= θ₀•cos(ωt-α)