# CAS Equation Writer

The HP 40g Equation Writer enables you to type expressions that you want to simplify, factor, differentiate, integrate, and so on, and then work them through as if on paper. The {CAS} key on the home menu bar takes you into the Equation Writer, and the [HOME] key takes you back out to the HP 40gs Home View Screen. The Equation Writer is a very efficient editor for writing, simplifying and transforming mathematical expressions. When you type expressions in the Equation Writer, the operator that you are typing always carries over to the adjacent or selected expression.

The Equation Writer is supplied with a menu bar of menus:

**TOOL** menu contains the commands:

- Cursor mode - enables you to go into cursor mode.
- Edit expr. - enables you to edit (modify) the highlighted expression.
- Change font - enables you to choose to type using large or small characters (you can make this choice at any time).
- Cut - copies the selection into the buffer, then erases the selection.
- Copy - copies the selection into the buffer.
- Paste - copies the buffer to the location of the cursor (the buffer containswhatever was selected the last time Copy or Cut was chosen).

**ALGB** menu contains functions that enable you to perform algebra: factoring, expansion, simplification, substitution.

COLLECT, DEF, EXPAND, FACTOR, PARTFRAC, QUOTE, STORE, | , SUBST, TEXPAND, UNASSIGN.

**DIFF** menu contains functions that enable you to perform differential calculus: differentiation, integration, series expansion, limits.

DERIV, DERVX, DIVPC, FOURIER, IBP, INTVX, LIMIT, PREVAL, RISCH, SERIES, TABVAR, TAYLOR0, TRUNC.

**REWRI** menu contains functions that enable you to rewrite an expression in another form.

DISTRIB, EPSX0, EXPLN, EXP2POW, FDISTRIB, LIN, LNCOLLECT, POWEXPAND, SINCOS, SIMPLIFY, XNUM, XQ.

**SOLV** menu contains functions that enable you to solve equations, linear systems, and differential equations.

DESOLVE, ISOLATE, LDEC, LINSOLVE, SOLVE, SOLVEX.

**TRIG** menu contains functions that enable you to transform trigonometric expressions.

ACOS2S, ASIN2C, ASIN2T, ATAN2S, HALFTAN, SINCOS, TAN2CS2, TAN2SC, TAN2SC2, TCOLLECT, TEXPAND, TLIN, TRIG, TRIGCOS, TRIGSIN, TRIGTAN.