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My teacher hasn't taught the topic yet, but thinks we can do this without any guidance. Can you please help.

 May 6, 2018
 #1
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+2

Both questions begin by making use of the Pythagoras theorem.

For the first one, start by saying that 9^2 + r^2 = (6 + r)^2, tidy up and solve for r.

The second one is asking you if the triangle is rightangled (Pythagoras again), if it is then ST will be a tangent.

 May 6, 2018
 #2
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Q1:

 

(6+r)2 = 92 + r2 

62 + 2*6*r+r2 =  92 + r2

62 + 2*6*r =  92 

2*6*r =  92 - 62

r = ( 92 - 6) / ( 2*6 )

 

Q2: 

by using pythagoras rule

if    RT2 = RS+ ST2    is true , ST is tangent to the circle.

 

         (5+8)2   =    5+ 122

           (13)2   =    5+ 122

            169    =    25 + 144

            169    =    169

yas 

 May 6, 2018
edited by Guest  May 6, 2018
 #3
avatar+51 
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Thank you very much for your help, you really helped me understand how to do these probelms. You're wonderful!

melvsky  May 6, 2018

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