simple harmonic with amplitude√a² + b²
not a simple harmonic
simple harmonic with amplitude ab
simple harmonic with amplitude (a+b)²
yresultant = y1 + y2 = asin(ωt) + bcos(ωt) = asin(ωt) + bsin(ωt + π/2)
Thus, the displacements are at right angles to each other.
∴amplitude of yresultant is √a² + b²