Geometry: Getting Started - Area of Polygons and Circles
This is a free lesson from our course in Geometry 
 
   
Rhombus
It is a quadrilateral with all the four sides equal in length.
(More text below video...)
<h2> Getting Started - Areas of Polygons and Circles - Watch video (Geometry)</h2> <p> area, measure, square, formula, video, area of polygons and circles, solution, geometry, square unit, example, practice questions</p> <p> If we are given the base of the triangle (b) and the perpendicular height (h); to calculate area use the formula: 1/2 x base x height</p>
Other useful lessons:
Area of a Rectangle
Area of a Triangle - Areas of Polygons and Circles
Area of a Square
Area of a Parallelogram
Area of a Trapezoid
Area of a Circle
Effect of dimension changes on Area
Real World Applications - Area of Polygons and Circles
(Continued from above) Properties and important points to remember-
• Rhombus is a special type of parallelogram, where all the four sides are the same length. It, however, has all the properties of a parallelogram.
• The diagonals of a rhombus always bisect each other at right angles i.e. form 90 at the point of intersection.
• The area of a rhombus equals to: (base * altitude). Other method could be to use length of diagonals i.e. 1 /2 times product of diagonals. Say d1 and d2 is the length of respective diagonal. Then area A = 1/2(d1 * d2).
Example 6 : Given- find the area of the rhombus, whose perimeter is 120 feet and one of its diagonal has a length of 40 feet.
Step 1: The perimeter is 120 ft (Given).
Step 2: To get sides of the rhombus divide by 4, which equals to 30 feet.
Step 3: You know that the length of the side OC of the right triangle is equal to half of the diagonal length i.e. it equals 20 ft.
Step 4: Now in right BOC, length of side BO can be calculated using Pythagorean Theorem i.e.202 + BO2 =302
Thus BO2 = (302 - 202).
It gives BO = 22.4 feet (rounded)
Step 5: Area the rhombus equals to 4 times the area of BOC i.e.
4 * [1/2*(22.4 x 20)].
Thus area of rhombus is 896 ft2, as the final answer.
 
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