** TI-84 Plus CE and TI-73 Explorer: Analog Clock**

**Introduction**

The program ANALOG draws a 12-hour analog clock for any given time, given the hour and minute. The TI-73 program covers the TI-73 Explorer and should be ported to any of the Texas Instruments calculators with monochrome screens with no or little adjustment.

The TI-84 Plus CE adds colors: hour hand is black, minute hand is brown, the markers are orange. Adjust colors to your liking.

**Notes**:

* The program pauses when the clock is drawn. Pressing [ENTER] restores turns the Axes back on.

* The Pt-On command has the syntax Pt-On(x, y, mark, color*). Mark: Dot (1 or default), Open Square (2), Plus (3). Color applies only to the TI-84 Plus CE or TI-84 Plus C Silver Edition.

* The program sets the calculator to degrees mode.

**Math**:

Let H be the hour and M be the minute.

Set S = H + M/60, where S is the decimal hour of the time given.

For a circle of 360°, each hour occupies 30° of the clock (360/12). Like wise, each minute occupies 6° of the clock (360/60).

A = 30*S, B= 6*M

Lines are drawn from the origin (0,0) to a point (x,y). If we set x and y to an angle θ, then:

x = r * cos θ, y = r * sin θ, where r is the length of the line.

Angels on a cartesian plane start from the positive x-axis and measured going counter-clockwise. However, on the analog clock requires angels to measured from the top (due north) and rotate clockwise. This will require a vertical flip and adjusting the angle by 90°. The adjusted coordinates are:

x = r * cos (θ-90°), y = -r * sin (θ- 90°), where r is the length of the line.

**TI-73 Program: ANALOG**

(this includes TI-73 Explorer)

"EWS 2021"

FnOff

PlotsOff

ClrDraw

Degree

Disp "12 HR ANALOG"

Input "HOUR? ",H

Input "MINUTE? ",M

ZStandard

ZSquare

AxesOff

Circle(0,0,8)

For(X,30,360,30)

Pt-On(7*cos(X-90),-7*sin(X-90),2)

End

Line(0,0,5*cos(30H+M-90),-5*sin(30H+M-90))

Line(0,0,7*cos(6M-90),-7*sin(6M-90))

Pause

AxesOn

**TI-84 Plus CE Program: ANALOG**

"EWS 2021-01-18"

FnOff

PlotsOff

ClrDraw

Degree

Disp "12 HOUR ANALOG CLOCK"

Input "HOUR? ",H

Input "MINUTE? ",M

ZStandard

ZSquare

AxesOff

GridOff

"FACE"

Circle(0,0,8,MEDGRAY)

For(I,30,360,30)

Pt-On(7*cos(I-90),7*sin(I-90),2,ORANGE)

End

"HOUR"

Line(0,0,5*cos(30H+M/2-90),5*sin(30H+M/2-90),1,BLACK)

"MINUTE"

Line(0,0,7*cos(6*M-90),7*sin(6*M-90),1,BROWN)

Pause

AxesOn

Next week, more fun with the TI-73 Explorer.

Eddie

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