temp.mw

I have this two expresions

e1 := (1/2)*P[psi]^2/(cos(`ϑ`)^2*Ix)

e2 := (1/2)*P[psi]^2/(cos(`ϑ`)^2*Ix)

simplify(e1-e2)=-(1/2)*(-P[psi]^2+P[psi]^2)/(cos(`ϑ`)^2*Ix)

but 

simplify(-P[psi]^2+P[psi]^2)

is zero 

why i dont obtain zero if i use simplify(e1-e2) ??

How can I expand exp(I x) to sin(x)+I*cos(x)

I use "cat" to concatinate greek letters but the output is not correct.test_cat.mw
 

Download test_cat.mw

I use WINDOW 10 

for j from 1 to 3 do
pout := cat("C:/Users/Eli/Documents/Animation/", "file", j, ".bmp"):
print(pout):
plotsetup(bmp, plotoutput = pout):
# plot (...)
od: