HP -28S Quick Reference
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HP-28S
0.693+0.5*Y—0.125*Y^2+4.166E-2*Y^3
Now convert back to a function of X:
…'X' PURGE 'X-2' 'Y' STO EVAL returns:
0.693+0.5*(X-2)—0.125*(X-2)^2+4.166E-2*(X-2)^3
For a test evalue this function for X=2.5:
…2.5 'X' STO EVAL returns 0.9171055…
The true value would be ln(2.5)=0.916290…
ISOL Isolates the leftmost occurence of a specified variable.
Example with flag 34 (principal value) set:
'A=3^(X+5)' 'X' ISOL returns 'LN(A)/1.0986…-5'.
'x^2=3^(X+5)' 'X' ISOL returns '√(3^(X+5))'.
'3^(X+5)=x^2' 'X' ISOL returns 'LN(X^2)/ 1.0986…-5'.
Example with flag 34 (principal value) clear:
'A=3^(X+5)' 'X' ISOL returns
'(LN(A) +2*π*i*n1)/1.0986…-5' where n1 is a placeholder for an
arbitrary integer number.
'x^2=3^(X+5)' 'X' ISOL returns 's1*√(3^(X+5))'.
'3^(X+5)=x^2' 'X' ISOL returns
'(LN(X^2)+2*π*i*n1)/ 1.0986…-5'.
QUAD See SOLV Menu.
SHOW Makes implicit references to a variable visible.
Example: Assume variable A contains the expression 'X+Y' and B contains a
plain number. Then 'A*B' 'X' SHOW returns '(X+Y)*B'.
The implicit reference of A*B to variable X is resolved in the result of SHOW.
Note that you could also use EVAL on 'A*B' but if A, X or Y contained
numerical values these would replace their variable names!
OBGET Returns the n-th object from an equation or expression:
'XX*LN(Y)=CCC' I OBGET returns for I=1…6:
{XX}, {*}, {LN}, {Y}, {=}, {CCC}
See also SIZE above.
EXGET Returns the n-th partial expression from an equation or expression:
'XX*LN(Y)=CCC' I EXGET returns for I=1…6:
'XX', 'XX*LN(Y)', 'LN(Y)', 'Y', 'XX*LN(Y)=CCC', 'CCC'
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