<PRE><B>Question 55629</B>
180=Angle #1+ Angle#2 + Angle#3 [Angle measures of a triangle]
Two of the angles of an isoceles triangle are equal.
Angle #1 = x
Angle #2=x
Angle #3=vertex angle =(x+x-40)
.
So,
180=x+x+(x+x-40)
180=4x-40
180+40=4x-40+40
220=4x
55=x
.
180=55+55+(55+55-40) [Plug all of the values back into the orginal formula]
180=180 [checks out]</PRE>