HP 40gs User Manual page 224

TEXPAND
14-42
TCOLLECT linearizes this expression in terms of sin(n x)
and cos(n x), then (in Real mode) reconstructs the sine and
cosine of the same angle.
Typing:
TCOLLECT(SIN(X) + COS(X))
gives:
π
⎛
⋅
-- -
2 cos x –
⎝
4
Develop transcendental expressions
TEXPAND has as an argument a transcendental
expression (that is, an expression with trigonometric,
exponential or logarithmic functions). TEXPAND develops
this expression in terms of sin(x), cos(x), exp(x) or ln(x).
Example 1
Typing:
TEXPAND(EXP(X+Y))
gives:
exp(x)·exp(y)
Example 2
Typing:
TEXPAND(LN(X·Y))
gives:
ln(y) + ln(x)
Example 3
Typing:
TEXPAND(COS(X+Y))
gives:
cos(y)·cos(x)–sin(y)·sin(x)
Example 4
Typing:
TEXPAND(COS(3·X))
⎞
⎠
Computer Algebra System (CAS)