Planimeter Applet
Try This!

Select "data/us.jpg" from the drop down box at the middle right.

Wait a long time for it to download.

Scroll the map down until you see the scale for the continental U.S.

Select the "ruler" checkbox.

Drag the mouse from the beginning of the scale to the end (500 miles)

Click on the text box after "ruler", and enter "500"

Click on the "scale name" checkbox.

Click on the text box after "scale name" and enter "miles". (Technically,
this particular text box is a placebo.)

Scroll the map until you see Ohio.

Click on the "move" checkbox.

Click the mouse about 1/3 of the way from Springfield IL toward Chicago.

Click on the "clear and trace" checkbox.

Trace the outline of Ohio (press the mouse button somewhere on the perimeter
of Ohio and then move the mouse around the perimeter while holding the
button down and be careful to finish at your starting point.)

Look at the value in the text box after "wheel reading." The number
there should be about 40000.

The area of Ohio is 41,222 square miles.

Structure of the Instrument

The Wheel

Tracer Arm Movement

Tracer Arm Rotation

Doubling Back Movement

Position of the Pivot

Path of the Pivot

Measuring Twice or in the Opposite Direction

The Zero Circle

Mathematical Definitions

Areas Measured

Corrections for Rotation of the Tracer Arm

Mathematical Expressions of Areas

Formula for Area

Formula for the Zero Circle

Proof of the Zero Circle

Formula for the Wheel Reading

Description of the Wheel Reading

Significance of the Wheel Reading

Geometric Interpretation of the Wheel Reading

Purpose of the Java Applet

Organization of the Applet Window

Colors in the Drawing Area

Some Areas Not Represented

Table of Area Colors

Planimeter Consists of Narrow Lines

Numeric Values of Areas

Selection of the Sample

Selection of the Drawing Mode

Tracing in the Drawing Area

Tracing Modes

Clearing

Move and Resize Modes

Resize Modes

Resizing Effects in the Drawing Area and Textboxes

Negative Numbers in Textboxes Implement Special
Features

Scaling Modes

Ruler Mode
Larry
Leinweber, Proprietor
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