Engineering
Mathematics
Line and Circle
Question

The sum of squares of the lengths of the chords intercepted on the circle, x2 + y2 = 16, by the  lines, x + y = n, n ∈ N, where N is the set of all natural numbers, is

160

210

105

320

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Solution

Equation of the circle: x2 + y2 = 16

Equation of the chord: x + y = n , n ∈ ℕ

Length of the chord: L = 2 16 - n2 2

Square of the length of the chord: L2 = 2 ( 32 - n2 )

Possible values of n: 1, 2, 3, 4, 5

Sum of squares of the lengths of chords:

2(31) + 2(28) + 2(23) + 2(16) + 2(7) = 210