Geometryhard · Past Paper
If a line y = mx + c is a tangent to the circle x^2 + y^2 = a^2, then c is equal to:
Aa * sqrt(1 + m^2)
Ba / sqrt(1 + m^2)
C+/- a * sqrt(1 + m^2)
D+/- a / m
✓ Correct Answer: C — +/- a * sqrt(1 + m^2)
The condition for tangency to a circle centered at origin is c^2 = a^2(1 + m^2).
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