Chapter 2: Main Application 52
Condition Judgment (judge, piecewise)
u “judge” Function
The “judge” function returns TRUE when an expression is true, and FALSE when it is false.
Problem Operation
Is the following expression true or false?
1 = 1 TRUE
[judge] 1 = 1 w
Is the following expression true or false?
1 < 0 FALSE
[judge] 1 < 0 w
u “piecewise” Function
The “piecewise” function returns one value when an expression is true, and another value when the expression
is false.
The syntax of the “piecewise” function is shown below.
piecewise(<condition expression>, <return value when true>, <return value when false or indeterminate> [ ) ]
or
piecewise(<condition expression>, <return value when true>, <return value when false>, <return value when
indeterminate> [ ) ]
Use the soft keyboard (1) to input “piecewise” function according to the syntax shown below.
or
<return value when true>, <condition expression>
<return value when false or indeterminate>
<return value when condition 1 is true>, <condition 1 expression>
<return value when condition 2 is true>, <condition 2 expression>
Problem Operation
For the expression 0 t
x ( x = variable), return 1
when x is 0 or less, and 2 when x is greater than 0
or undefined.
[piecewise] 0 :X, 1 , 2 w
or
1 1 c 2 ef 0 :X w
For the expression 1 t
x ( x = variable), return 1
when x is 1 or less, and 2 when x is greater than 1.
1 1 c 2 ef 1 :X c 1 <Xw
Angle Symbol (∠)
Use this symbol to specify the coordinate format required by an angle in a vector.
You can use this symbol for a vector only.
Problem Operation
Convert the polar coordinates
r = '2 ,
θ
= π /4 to
rectangular coordinates. [1, 1]
Change the [Angle] setting to “Radian”.
[toRect] [5 2 e,~7/ 4 )]w
Derivative Symbol (’)
A single derivative symbol indicates the first derivative of an equation in the format: <variable name>’.
Problem Operation
Solve the differential equation
y ’ = x .
{ y = 0.5 · x
2
+ const (1)}
+Y'=X,X,Yw
Important!
The “dSolve” function can solve differential equations up to three degrees, so a maximum of three derivative
symbols ( y ’’’) can be used. Executing a “dSolve” calculation that has more than three derivative symbols will
result in an Invalid Syntax error.
