D Values and Variables

GrafEq has three main groups of values and variables: numbers, Roman letters, and Greek letters.

D.1 Numbers

Numbers are formed from the ten numeric digits (0 to 9), the decimal point, and the negation sign. Numbers are always numeric constants. Digits cannot be used as variables.

Numbers can be entered via the computer keyboard, the numeric key pad, or by using the easy button floating window.

Tip: Infinity (∞) can be entered by pressing control-8 in GrafEq.

D.2 Roman Letters

All Roman letters except e can be used as variables or constants. GrafEq predefines e as 2.7182818284590452..., the base of natural logarithms. GrafEq is case sensitive, so upper- and lower-case letters are considered different and unique; x and X are not the same.

Roman letters can be entered via the computer keyboard or by using the easy button floating window.

D.3 Greek Letters

All Greek letters except π can be used as variables or constants. The Greek letter π is a predefined constant in GrafEq, equal to 3.1415926535897932..., and is a half circle’s angle in radian measure. GrafEq is case sensitive, so upper- and lower-case letters are not the same; ω and Ω are two different variables.

Greek characters can be entered via the easy button floating window, by typing in their name, or by using the keyboard key combinations listed in figure D.1. For example, “α” may be entered by clicking on the appropriate easy button, by typing “alpha”, or by pressing control-a.

Alpha	Α	control-A	α	control-a
Beta	Β	control-B	β	control-b
Chi	Χ	control-C	χ	control-c
Delta	Δ	control-D	δ	control-d
Epsilon	Ε	control-E	ε	control-e
Phi	Φ	control-F	φ	control-f
Gamma	Γ	control-G	γ	control-g
Eta	Η	control-H	η	control-h
Iota	Ι	control-I	ι	control-i
Theta variant	ϑ	control-J
Phi variant			ϕ	control-j
Kappa	Κ	control-K	κ	control-k
Lambda	Λ	control-L	λ	control-l
Mu	Μ	control-M	μ	control-m
Nu	Ν	control-N	ν	control-n
Omicron	Ο	control-O	ο	control-o
Pi	Π	control-P	π	control-p
Theta	Θ	control-Q	θ	control-q
Rho	Ρ	control-R	ρ	control-r
Sigma	Σ	control-S	σ	control-s
Tau	Τ	control-T	τ	control-t
Upsilon	Υ	control-U	υ	control-u
Sigma variant	ς	control-V
Pi variant			ϖ	control-v
Omega	Ω	control-W	ω	control-w
Xi	Ξ	control-X	ξ	control-x
Psi	Ψ	control-Y	ψ	control-y
Zeta	Ζ	control-Z	ζ	control-z

Figure D.1: Greek Alphabet and corresponding input key combinations

D.4 Sets

Sets can be discrete or continuous. A discrete set contains elements listed within a pair of braces: for example, {2,5} or {x,sinx}. A continuous set can either contain open ranges described within a pair of parentheses, or closed ranges described within a pair of square brackets: for example, (0,1) or [-1,4]. Combinations, such as {1,[2,x]} and {(1,4],cosy}, are certainly possible.

Conclusion

To review:

• GrafEq relations can be specified in a wide latitude.
  • Almost any letter is accepted as a variable name.
  • In the Create View window any letter entered in a relation window can be chosen as a domain or range variable; x, y, r, and θ are always available as choices.
  • For cartesian (rectangular) graphs, domain (horizontal axis) and range (vertical axis) variables default to x and y; for polar graphs, θ and r.
  • In both cartesian and polar graphs, r defaults to the distance from the origin, and θ to the position angle in radians.
• Each variable is a single letter; xy is the product of two variables and cannot be used as a variable name.
• Some letters are reserved by GrafEq (namely, π, e, and ∞) and cannot be used as variables.

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