Either of these three ways is correct.  The first way is like the
tutor above did it.  The second way gives the same answer in the
same form.  The last one is in a different form but it is 
equal to the other one.

sin(75°) = sin(45°+30°) = sin(45°)cos(30°)+cos(45°)sin(30°) = ( =  =  

sin(75°) = sin(120°-45°) = sin(120°)cos(45°)-cos(120°)sin(45°) = ( = ( =  

sin(75°) = sin() =  =  =  =  =  = 

Edwin