HP -28S Quick Reference
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HP-28S
The presence of the following commands depends on the type of the current
subexpression:
E() Replace exponentials of an exponent by a product of exponentials:
EXP(A)^B → EXP(A*B)
E^
Inverse of E(): EXP(A*B) → EXP(A)^B
←D Distribute left. A*(B+C) → (A*B)+(A*C)
D→
Distribute right.
←A
Associate left. This moves the grouping brackets to the left.
A→
Associate right. This moves the grouping brackets to the right.
←M
Collect similar right-hand-side factors of surrounding expressions.
M→
Collect similar left-hand-side factors of surrounding expressions.
DNEG Insert a double-negation.
DINV Insert a double inversion.
*1 Insert multiplication by 1.
/1 Insert division by 1.
^1 Insert exponentiation by 1.
+1-1 Insert addition of +1-1.
→()
Distribute a prefix-operator (ie. minus sign, INV()) into the following
sub-expression.
-()
Combination of DNEG and a →() of the inner negation.
1/()
Combination of DINV and a →() of the inner inversion.
←→
Swap left and right side of operator. Inserts a factor –1 or 1/x when
executed on substraction or division.
L* Replace logarithm of an exponential by a product of a logarithm and
the exponent: LN(A^B) → (LN(A)*B)
L()
Inverse of L*: (LN(A)*B) → LN(A^B)
AF Add fractions by expanding to a common denominator.
OBSUB Replaces the n-th object with a new one. See also OBGET below:
'XX*LN(Y)=CCC' 4 {Q} OBSUB returns 'XX*LN(Q)=CCC'.
'XX*LN(Y)=CCC' 5 {Q} OBSUB returns 'Q(XX*LN(Q),CCC)'.
'XX*LN(Y)=CCC' 1 {-} OBSUB returns an error.
EXSUB Replaces the n-th expression with a new one. See also EXGET below:
'XX*LN(Y)=CCC' 3 '2*K' EXSUB returns 'XX*(2*K)=CCC'.
TAYLR Calculates a Taylor series (polynomial) for an arbitrary function. Example:
'X/(X^2+1)' 'X' 3 TAYLR returns 'X-X^3'.
'SIN(X)' 'X' 5 TAYLR returns 'X-0.1666*X^3+8.3333E-3*X^5'.
The series is developed around X=0 which may not always be desirable.
To shift the point of expansion, ie. from X=0 to X=2:
• Store 'Y+2' in variable X. Make sure variable Y does not exist.
• Evaluate the function f(X) to convert it to a function f(Y).
• Perform the Taylor series expansion for Y.
• Evaluate the resulting function around Y=0 or:
• Store 'X-2' in variable Y. Make sure variable X does not exist.
• Evaluate the Taylor series to convert it into a function of X.
• Evaluate the result for values of X around 2.
Example: Develop ln(x) around x=2:
'LN(X)' 'Y+2' 'X' STO EVAL returns f(y)=LN(Y+2).
…'Y' 3 TAYLR returns the expansion around Y=0:
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