Quite a number of students have difficulty understanding R formula.
Hopefully this graph will help.
So the two graphs appear as 1 graph.
Max value of 3 sin(x)+4 cos (x) = 5. Occurs when sin(x+0.927)=1
Min value of 3 sin(x)+4 cos (x) = -5. Occurs when sin(x+0.927)=-1
Students can try their hands in R formula at https://www.desmos.com/calculator