NetGX! Posted March 24, 2004 Share Posted March 24, 2004 For some strange reason my other account is not coming up.. "NetGX™" it says that it cannot find that username... anyway i'll sort that out later. I have this maths problem and I can't finish it. My teacher is going to be away for a while so I can't ask him. I've sat it four about 2 hours and still I can't get it out here it is anyway Anyhelp would be appreciaed Link to comment Share on other sites More sharing options...
m0fo Posted March 24, 2004 Share Posted March 24, 2004 i) since ECF is tangent to the circle, we can prove that angle DCE = angle DBC angle DBC is across from chord DC which is also across from angle DAC... therefore angles DAC and DBC are equal if DA = DC, then opposite angles from equal chords are equal and thus DAC = DCA from above, DCE = DBC = DAC = DCA, therefore DCE = DCA, and thus DC is bisecting angle ACE ii) since DC = DA, the opposite angles of each chord are equal (angle ACD = angle CBD)... also DB = DB since they are teh same chord therefore, triangle DAB = triangle DCB by Side-Angle-Side knowing that triangles DAB and DCB are equal, we know that AB = CB and also angle ABD = angle CBD since GB = GB, we can now prove that triangle AGB = triangle CGB (by side[ab=cb]-angle[abd=cbd]-side[gb=gb] once again) now, since triangles AGB and CGB are equal, we know that AG = GC since chord DB bisects chord AC (since AG = GB), AC is perpendicular to DB iii) DCE = 25 (given) DCE = DBC (proven above using tangents) therefore DBC = 25 degrees angle DCB is a right angle since its hypotenuse is the diameter therefore, angle ECB = 25 + 90 = 115 degrees angles in a triangle is 180 which means angle DEC = (180 - DBC - ECB) = 180 - 25 - 115 = 40 degrees Link to comment Share on other sites More sharing options...
NetGX Posted March 24, 2004 Share Posted March 24, 2004 Thanx alot mate.. It really really helped. I truly am very grateful. Cheers Link to comment Share on other sites More sharing options...
dL Posted March 24, 2004 Share Posted March 24, 2004 Haha! I'm doing that right now in school, test this Thursday. Link to comment Share on other sites More sharing options...
NetGX Posted March 24, 2004 Share Posted March 24, 2004 LOL, how are you going with it.. My test is next wednesday. I've got most of it figured out now. Link to comment Share on other sites More sharing options...
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