A maths - plane geo

• bonkysleuth

  10 May 09, 22:57

  

  Triangle ABC is inscribed in a circle where angle A is bisected by AD and triangle BCD is an isoceles triangle. A tangent to the circle is drawn at D meeting AC produced at E. Show that BD^2 = (AB)(CE)

   

  really can't see the pattern. please help. thank you.

• wee_ws

  11 May 09, 06:13

  Hi,

    Can you see that triangles ACD and DCE are similar?

    Thanks!

  Cheers,
  Wen Shih

• bonkysleuth

  11 May 09, 09:22

  Originally posted by wee_ws:

  Hi,

    Can you see that triangles ACD and DCE are similar?

    Thanks!

  Cheers,
  Wen Shih

  
  yea i can. I know how to derive the answer from there but I can only find a similar angle for the 2 triangles... Is there some other way to prove that the 2 triangles are similar? thank you.

• SBS261P

  11 May 09, 10:39

  angle CDE = angle DAC

  angle ADC = 90 - angle CDE =-> angle ACD is 90 => angle DCE is 90.

  den proceed lor...