
Answer:
Ф = 142.674 degree
Ф = 2.490131057 rad
wavelength  = 0.396316 λ
Explanation:
Given data
combined wave having an amplitude 0.64 times
to find out
answer in degrees, Â radians, and fraction of the wavelength
solution
let us consider these two wave equation
Asin(ωt) and the Asin (ωt + Ф)
and here Ф is phase difference
so we say
resultant wave is
Y = Asin(ωt) + Asin (ωt + Ф) =  Asin(ωt + Ф/2) cos ( Ф/2)
so Y = A' sin(ωt + Ф/2)
we know that here resultant wave amplitude is 2A cos ( Ф/2)
so
put A= 0.64 A
so 2Acos ( Ф/2)  = 0.64 A
and Ф/2  = 71.3370
Ф = 142.674 degree
Ф = 2.490131057 rad
so wavelength is  2.490131057 /  2π
wavelength  = 0.396316 λ