In a triangle ABC, D is the midpoint of BC. Join AD. Angle ADB = 45 degree and angle ACB = 30 degree. Find angle ABC.
(In reply to
re(2): Solution  This is how long it took me: by Eric)
I worked the the problem on Geometer's Sketchpad.
Since the measured angle was 105 degrees exactly
and it easily satisfies the equation
2 cos(15) 1
 = 
sin(?) sin(135?)
I didn't think to write out the derivation.

Posted by Bractals
on 20060225 18:20:55 