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Grade 11Analytical Geometry

the line Ax+By+C=0 will touch the circle x^2+y^2=lamda when????
answer is given as C^2=lamda(A^2+B^2)

Profile image of prasad
8 Years agoGrade 11
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1 Answer

Profile image of Pradeep Tangirala
8 Years ago
Ax+By+C=0 touches the circle means...it is a tangent....Now, radius of circle is equal to (lamda)*1/2...and its centre is (0,0)...now distance from centre to line is equal to |C|÷(A*2+B*2)*1/2.....which is equal to radius, (lamda)*1/2...so....|C|÷(A*2+B*2)*1/2 =(lamda)*1/2...now 
Squaring on both sides...you will get the ans....