Question

if you are asked to graph 2 sin (pi/2)x. How do you know what to scale your graph by?

Answer 1

if your format is like your saying.. then only sin only goes up to 1... multiply that by 2... so plus or minus 2... then for your period of the sin function.. you are halving your wave..

Answer 2

This is mostly arbitrary, but since y ranges from -2 to 2 and the domain of x is unbounded, your y axis should range beyond +/- 2 and the x axis should include a couple periods of the wave so like +/- 4