The correct option is A 5
Given:
Y1=5sin(ωt−kx) and Y2=−5cos(ωt−kx−150∘)=5sin(ωt−kx−240∘)
Y=Y1+Y2
where Y is the resultant wave
The amplitude of this resultant wave is given by the formula
A=√(A1)2+(A2)2+2A1A2cosϕ
Here,
A1=5,A2=5 and ϕ=240∘
On substituting the values on the given formula
A=√(5)2+(5)2+2×5×5cos(150∘)
=√25+25−2×25×12 (∵cos 240∘=−12)
Hence, A=5