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1.2 Arc Length & Area of The Circle

Arc length

O is the centre of the circle of radius 'r' (r > 0) . A central angle of qc radians intercepts an arc AB of length 's'. We know that angle subtended at the centre (is proportional to the ) length of the arc.

\ qc = K . s .....(1)

where K is a constant.
Let `C' be any point on this circle such that Ð BOC = 1 radian so that length of arc BC = r

\ 1c = K . r .....(2)

Comparing the two relations (1) and (2) we have =



Note : In this formula q is always in radians with r and s are measured in the same units of length.

But when qis measured in degrees,

For military purpose this written as W = Rm where m is the central angle in mils. R is the radius (range) expressed in thousands of meters and W is the chord (width) expressed in meters.


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Index

1.1 Angles (Radians & Degrees)
1.2 Arc Length & Area of the circle
Supplementary Problems

Chapter 2