180 Part 3: The Shape of the World
CHECK POINT- Find the area of a triangle with a base 14 cm long and an altitude of 7 cm.
- If the area of a triangle is 27 square inches, and the altitude measures 6 inches,
how long is the base to which that altitude is drawn? - Find the perimeter of a right triangle with legs that measure 20 cm and 48 cm.
- Find the perimeter of an equilateral triangle with an area of^93 square inches.
- The area of a right triangle with legs of 3 cm and 4 cm and hypotenuse of 5 cm
is __ square centimeters, so the altitude from the right angle to the hypot-
enuse is __ centimeters long.
The Least You Need to Know
- Equilateral triangles have three sides of equal length, isosceles triangles have two
sides of equal length, and scalene triangles have no equal sides. - Obtuse triangles contain one obtuse angle, right triangles contain one right angle,
and acute triangles have three acute angles. - In any right triangle, the sum of the squares of the lengths of the legs is equal to
the square of the length of the hypotenuse. - In a 30-60-90 right triangle, the shorter leg is half the length of the hypotenuse
and the longer leg is half the hypotenuse times the square root of three. - The perimeter of any polygon is the sum of the lengths of its sides.
- The area of a triangle is one-half the length of the base times the height.