How to draw graph of y=2cos(x+60).

Answer 1

I would suggest using "desmos" free on line graphing program and just graphing
1) cosx
then
2) 2cosx
then
3) 2cos(x+60)
because that way you will see the change in the amplitude and phase shift : )

Answer 2

Wolfram, one of the better apps for math, makes it quite easy
to follow Ms Pi's suggestion

https://www.wolframalpha.com/input/?i=plot+y+%3D+cosx%2C+y+%3D+2cosx%2C+y+%3D+2cos%28x%2B%CF%80%2F3%29