1. Objectives: 1. To find the perimeter or circumference of basic shapes 2. To find the area of basic shapes

2. K EY WORDS 1. Perimeter 2. Circumference 3. Area 4. Triangles 5. Rectangles 6. Circles 7. Polygons

3. Real life example

4. Bermuda Triangle

5. Importance of triangle in engineering Engineers believe that triangle is the strongest shape of any other polygon in constructing buildings.

6. Perimeter of a triangle Add the lengths of all three sides. The sum is called perimeter of triangle. Example 1

7. Example 2 The Bermuda Triangle supposedly causes trouble for aircraft pilots. It has a perimeter of 3075 mi. The shortest side measures 75 mi less than the middle side, and the longest side measures 375 mi more than the middle side. Find the lengths of the three sides.

8. Practice/Homework Textbook page 64 Problems: 14, 15

9. AREA OF THE TRIANGLE

10. Find the area of a real triangle Activity: step 1: take a string step 2: make a triangle step 3: find its area. repeat the activity by making a different kind of triangle. determine the lengths of the sides of triangle for which area is maximum. Do you see any relationship between kind of triangle and its area? Note: do not change the length of the string.

11. A B C DE F A = (0, 0), B= ( 6, 10) C= (-4, 2)

12. sum of three angles in a triangle Activity: Draw a triangle Cut out the triangle Cut out the three angles of triangle Place the angles along a straight line Conclude the sum of three angles is 180 degrees.