Circles, Mathematics

If the distances from origin of the centres of 3 circles x2+y2+2alphaix= a2 (i=1,2,3) are in G.P. , then length of the tangents drawn to them frm any point on the circles x2+y2 = a2 are in :

(a) A.P (b) G.P (c) H.P (d) None of these


Ans)   C

centres of the 3 circles are (-alphai,0) (i= 1,2,3)

Distances of thes from origin are alpha1, alpha2, alpha 3

now (alpha2)^2= (alpha1)(alpha3)

Also general point on  x2+y2=a2 is (a costheta, a sintheta) length of tangent from this point on the given circle is

sqrt( (a cos theta)2+(a sintheta)2 +2alphai(a costheta) -a2)) = sqrt ( 2alphai(a costheta))

now as alpha 1, alpha 2, alpha 3 are in GP

then sqrt alpha 1, sqrt alpha 2, sqrt alpha 3 are in gp

then sqrt 2acos theta alpha 1 , 2acos theta alpha 2 and sqrt 2acos theta alpha 3 are also in GP

Posted Date: 3/11/2013 7:33:13 AM | Location : United States







Related Discussions:- Circles, Assignment Help, Ask Question on Circles, Get Answer, Expert's Help, Circles Discussions

Write discussion on Circles
Your posts are moderated
Related Questions
what is 1/5 + 1/8 equals?

Q. Define Combined Functions? Ans. We are often interested in functions which combine a trigonometric function with another type of function.  For example, y = x + sinx wi

3 9/10 into decimal

evaluate limit as x approaches 0 (x squared times sin (1/x)

A survey of 400 of recently qualified chartered Accountant revealed that 112 joined industry, 120 stated practice & 160 joined the firms of practicing chartered accountants as paid

rational number as decimal and check


Find the center and radius of the circle whose equation is 3 x^2 - 8 x+ 3 y^2+ 4 y+ 2 = 0