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Hiii im new here and i really need some answers huhuhu :((

 

How can you find the equation of a tangent if there is no given point?? Our teacher gave us an item to solve about equation of a tangent and she gave us

 

x^2+y^2+6x-10y+17=0

 

I hope you can help meeeee :( 

 Jul 4, 2016
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This is the graph of a circle.......if you have had calculus, we can use implcit differentiation to find the slope of a line that is tangent to the circle at any point (x, y)......this is given by :

 

 

x^2+y^2+6x-10y+17=0           implicitly differentiate

 

2x + 2yy' + 6 -10y' + 0 = 0  

 

y' [ 2y -10 ]   =  - [ 2x + 6]      divide through by 2

 

y' [ y - 5]  = - [ x + 3]      divide by [ y - 5]

 

y'  = - [ x + 3] / [ y -5]       factor out a  -1

 

y' = [ x + 3] / [5 - y]         the right side is the slope of the tangent line for any (x , y)  on the circle.....so......you can use this slope and the point to write an equation for a tangent line just like you would in Algebra !!!........note that the slope is undefined when y = 5

 

 

 

cool cool cool

 Jul 4, 2016

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