State whether the statements True or False. Justify
If the line lx + my = 1 is a tangent to the circle x2 + y2 = a2, then the point (l, m) lies on a circle.
lx + my = 1
my = 1 – lx
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Slope of tangent = -l
x2 + y2 = a2
(x – 0) 2 + (y – 0) 2 = a2
Centre = (0, 0) Radius = a units
Slope of line perpendicular to tangent=
{Product of slopes of perpendicular lines = -1}
Equation of line perpendicular to tangent i.e.., Radius of the circle
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ly = x – 0
Distance of centre (0,0) from the line lx + my = 1 is equal to the radius ‘a’.
Perpendicular Distance (Between a point and line) =
, whereas the point is
and the line is expressed as ax + by + c = 0
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Squaring both the sides,
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Hence, the locus of (l,m)is
, which is a circle.
TRUE
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