Solve? (1 Viewer)

[ayehann]

find the values for K for which L is a tangent to C





that is the equation for line L


i know that C is a cricle with radius 5 and centre (2,-3)
and the perpendicular length from centre of circle to line L is

 

[Drongoski]

find the values for K for which L is a tangent to C





that is the equation for line L


i know that C is a cricle with radius 5 and centre (2,-3)
and the perpendicular length from centre of circle to line L is

All you need do is:

substitute y = (k-3x)/4 into the other eqn (u don't even need to realise it is a circle) and u end up with a quadratic eqn in x. Then u apply the condition: the discriminant "b^2 - 4ac" of this eqn = 0. You end up with a quadratic eqn in k. Solve for this; there are 2 possible values for k reflecting the 2 tangents to the circle.

Edit

Excuse me, I did not read question carefully. What is the 'C' doing in the equation of the circle - shouldn't that be 0?

 

[Lukybear]

Sorry to bulge into thread, but how would one find the equation of a circle in the form of:

(x+a)^2 + (y+b)^2 i.e. from the above. Really curious.

 

[gurmies]

complete the square

 

[Drongoski]

Lukybear

 

[ayehann]

All you need do is:


Excuse me, I did not read question carefully. What is the 'C' doing in the equation of the crcle - shouldn't that be 0?

err yes... thats what i meanntt .. hehe

 

[Drongoski]

err yes... thats what i meanntt .. hehe

if ayehann is yr name it sounds turkish!