Question 117566
Let x=measure of angle 1, y=measure of angle 2, and z=measure of angle 3,


Since two angles are equal to one another (say the first two), this means that {{{y=x}}}. Now remember, the sum of the angles of a triangle is always 180 degrees. In other words, 



{{{x+y+z=180}}}



But remember, {{{y=x}}}. So we can replace y with x to get



{{{x+x+z=180}}}



{{{2x+z=180}}} Combine like terms



{{{z=180-2x}}} Subtract 2x from both sides to isolate z (which is the third angle)



So the third angle can be found through the formula


{{{z=180-2x}}} if the first two angles are equal.