#2)Sum and Diff of 2 Angles Trig Identities
var('y')
f(x)=sin(x+y)
show(f(x))
show(f(x).simplify_trig())
f(x)=sin(x-y)
show(f(x))
show(f(x).simplify_trig())
f(x)=cos(x+y)
show(f(x))
show(f(x).simplify_trig())
f(x)=cos(x-y)
show(f(x))
show(f(x).simplify_trig())