30 Section 2: Numeric Functions
For example, to find the sales tax at 3% and total cost of a $15.76 item:
Keystrokes Display
15.76 v
15.7600
Enters the base number (the price).
3 | k
0.4728
Calculates 3% of $15.76 (the tax).
+
16.2328
Total cost of item ($15.76 + $0.47).
Percent Difference. The ∆ function calculates the percent difference
between two numbers. The result expresses the relative increase (a
positive result) or decrease (a negative result) of the second number
entered compared to the first number entered.
For example, suppose the $15.76 item only cost $14.12 last year. What
is the percent difference in last year’s price relative to this year’s?
15.76 v
15.7600
This year’s price (our base number)
14.12 | ∆
-10.4061
Last year’s price was 10.41% less
than this year’s price.
Polar and Rectangular Coordinate Conversions
The : and ;
functions are provided in
the HP 15c for conversions between polar
coordinates and rectangular coordinates.
The angle θ is assumed to be in the units set
by the current trigonometric mode, whether
degrees (in a decimal format, not a
minutes-seconds format), radians, or
grads. θ is measured as shown in the
illustration at right.
Polar Conversion. Pressing | :
(polar) converts a set of rectangular coordinates (x, y) to polar
coordinates (magnitude r, angle θ). The y-value must be entered first, the
x-value second. Upon executing | :, r will appear in the display.
Press ® (X exchange Y) to bring θ out of the Y-register and into the
display (X-register). θ will be returned as a value between −180° and 180°,
between −π and π
radians, or between −200 and 200 grads.
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