Sector of a Circle

Divide the circle of radius 13 cm into four parts by two perpendicular chords, both 5 cm from the center. What is the area of the smallest part.

14 - Area the goat can graze inside a right triangular lot

A 30° right triangular lot has the long leg measuring 67 m. On the long leg and 15 m from the short leg, is a peg to which a goat is tied such that the farthest distance its mouth can reach is 30 m from the peg. Find the area inside the lot from which the goat can graze.



12 - Circular sector inscribed in a square

Problem 12
A circular sector of radius 10 cm is inscribed in a square of sides 10 cm such that the center of the circle is at the midpoint of one side of the square. Find the area of the sector in cm2.



06 Circular arcs inside and tangent to an equilateral triangle

Example 06
The figure shown below is an equilateral triangle of sides 20 cm. Three arcs are drawn inside the triangle. Each arc has center at one vertex and tangent to the opposite side. Find the area of region enclosed by these arcs. The required area is shaded as shown in the figure below.

Circular arcs inside a triangle


05 Three identical cirular arcs inside a circle

Example 05
Circular arcs of radii 10 cm are described inside a circle of radius 10 cm. The centers of each arc are on the circle and so arranged so that they are equally distant from each other. Find the area enclosed by three arcs shown as shaded regions in the figure.

04 Four overlapping semi-circles inside a square

Example 04
The figure shown below consists of arcs of four semi-circles with centers at the midpoints of the sides of a square. The square measures 20 cm by 20 cm. Find the area bounded by these circular arcs shaded in the figure shown.

03 Area enclosed by pairs of overlapping quarter circles

Example 03
The shaded regions in the figure below are areas bounded by two circular arcs. The arcs have center at the corners of the square and radii equal to the length of the sides. Calculate the area of the shaded region.

02 Area bounded by arcs of quarter circles

Three Different Ways of Finding the Area Bounded by Arcs of Quarter Circles

Example 02
Arcs of quarter circles are drawn inside the square. The center of each circle is at each corner of the square. If the radius of each arc is equal to 20 cm and the sides of the square are also 20 cm. Find the area common to the four circular quadrants. See figure below.

Area common to four quarter circles


01 Arcs of quarter circles

Example 01
The figure shown below are circular arcs with center at each corner of the square and radius equal to the side of the square. It is desired to find the area enclosed by these arcs. Determine the area of the shaded region.

Intersection of circular quadrants


The Circle

The following are short descriptions of the circle shown below.

Tangent - is a line that would pass through one point on the circle.
Secant - is a line that would pass through two points on the circle.
Chord - is a secant that would terminate on the circle itself.
Diameter, d - is a chord that passes through the center of the circle.
Radius, r - is one-half of the diameter.


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