Two waves
` y_(1) =A_(1) sin (omega t - beta _(1)), y_(2)=A_(2) sin (omega t - beta_(2)`
Superimpose to form a resultant wave whose amplitude is
A. ` sqrt(A_(1)^(2)+ A_(2)^(2)+2A_(1)A_(2)cos (beta_(1)-beta_(2)))`
B. ` sqrt(A_(1)^(2)+ A_(2)^(2)+2A_(1)A_(2)sin (beta_(1)-beta_(2)))`
C. `A_(1) +A_(2)`
D. `|A_(1) +A_(2)|`
