178 Part 3: The Shape of the World
CHECK POINT
16. 'ABC is a 30r-60r-90r right triangle, with hypotenuse 8 cm long. Find the
length of the shorter leg.- 'RST is an isosceles right triangle with legs 5 inches long. Find the length of
the hypotenuse. - 'ARM is a right triangle with AR = 14 meters, RM = 28 meters, and
AM = 14 3 meters. Find the mM. - 'LEG is a right triangle with LE = EG and LG = 72 inches. Find mG.
- 'OWL is an isosceles right triangle with OW > OL. Which angle is the right
angle?
Area and Perimeter
The perimeter of any figure is the distance around all the edges. In a triangle, that means the sum
of the lengths of the three sides. If a right triangle has legs of 3 feet and 4 feet and a hypotenuse
of 5 feet, its perimeter is 3 + 4 + 5 = 12 feet.DEFINITION
The perimeter of a triangle (or any polygon) is the total of the lengths of all its sides.If you know the perimeter and two of the sides of a triangle, you can work backward to find the
length of the other side. If a triangle has a perimeter of 42 inches, and you know that it has an
18-inch side and a 15-inch side, you can add 18 + 15 to find out that the two known sides account
for 33 inches of the perimeter, so the third side must be 42 – 33 = 9 inches long.
If you think of the perimeter as the outline of a shape, you can think of the area as the space
inside the perimeter. This is true for triangles and for all polygons. When you talk about the size
of a lot of land or the size of a rug, you’re talking about area.DEFINITION
The area of a polygon is the space enclosed within its sides.To find the area of a triangle, you need to know the measure of the base and the height. Then
you can plug these measurements into a simple formula, A^1 bh
2, where A = area, b = base, and
h = height. You can call any one of the sides the base, as long as the height is the length of the