This activity uses Cabri Jr. to discover that the angle between a tangent and a chord is equal to the inscribed angle on the opposite side of the chord.
Before the Activity
Students require activity sheet Cabri Jr. Tangent to a Chord
During the Activity
1. Draw a circle in the center of the screen. Use the Alpha Numeric Tool to label the center O.
Use the Point On Tool to make three points on the circle. Do not use the radius point of the circle as one of the points. Label the points A, B, and C. .
2. Draw a Tangent to the Circle at Point C.
Use the Segment Tool to draw a radius from the center of the circle to point C.
Select the Perpendicular Tool and move the arrow to radius OC. Once OC is shimmering press enter to select it. Move the pointer to Point C and press enter.
Use the Point On Tool to draw Point E on the perpendicular line.
Select the Hide/Show Tool and choose object to hide the radius OC.
3. Use the Segment Tool to draw chord AC.
Use the Measure Tool to find the measure of angle ACE.
4. Use the Segment Tool to draw an inscribed angle ABC .
Use the Measure Tool to measure angle ACE and record the angle measurement in the table.
After the Activity
Go over answers to the activity sheet.
Reteach as necessary.