# CAT Practice : Coordinate Geometry

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Substitute the value of external angle of an octagon and then continue!!

## Area of Rhombus

Q.21: Rhombus of side 6 cm has an angle equal to the external angle of a regular octagon. Find the area of the rhombus.
1. 18 $\sqrt{2}$cm2
2. 9 $\sqrt{2}$cm2
3. 15 $\sqrt{2}$cm2
4. 12 $\sqrt{2}$cm2

Choice (A).18 $\sqrt{2}$cm2

## Detailed Solution

Side of the rhombus 's' = 6 cm
Angle between sides 'a' = exterior angle of an octagon
Therefore a = 45 degrees
Area of rhombus = sin a * s2

Area = $\frac{1}{\sqrt{2}}$ * 36

Area = 18 $\sqrt{2}$cm2

Correct Answer: 18 $\sqrt{2}$cm2

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Geometry is probably the most vital topic as far as CAT preparation is concerned. Geometry sets the stage for Trigonometry, Cogeo and Mensuration as well.