Bradford T. answered 10/16/23
MS in Electrical Engineering with 40+ years as an Engineer
What you need to do is set the curves equal at the end points.
The first two equations match up when t = 0
2t+b =2cos(x)-3
b = 2(1) -3 = -1
The second and third equations match up when t = π/2
2cos(t)-3 = asin(t)+5b
2(0)-3 = a(1)-5
a = -2