MEASUREMENT OF THE INTERIOR ANGLES OF A TRIANGLE
BY
LINDA LaPERRE
If you were asked to measure a triangle, just exactly what would you
measure? Would you measure the length of the sides? What would you
have if you added up those lengths? (perimeter) Would you measure how
much space the triangle cover? (area?) Today, you are going to measure the
angles of the inside of a triangle. What unit will you use? (degrees) If you
add up the degrees of all three angles of the triangle what will you get?
Click here to go to the Geometer’s Sketchpad page and measure all three
angles. What is the sum of the three angles?
Next, grab “A” and move it around. What do you notice about the
measurement of the angles? Grab “B” and move it around. What do you
notice?
As you move “A”, then“B” and then “C”, what happens to the triangle?
How does the shape change? What conclusion can you make about the sum
of the interior angles of a triangle?