Question 1010014
What other measurements do you have?
Vertical angle?
Length of sides?
Height?
Area?
{{{drawing(300,300,-5,5,-1,9,
green(triangle(-4,0,0,0,0,8)),
green(rectangle(-0.4,0,0,0.4)),
triangle(-4,0,4,0,0,8),
red(arc(0,8,2,2,63.4,116.6)),
locate(0.05,7,red(B)),locate(-0.1,8.5,B),
locate(-4.3,0.3,A),locate(4.1,0.3,C),
locate(-2,4,c),locate(1.8,4,a),
locate(-2.2,0.6,"b / 2"),locate(1.8,0.6,"b / 2"),
locate(-0.1,-0.1,b),arrow(0.2,-0.4,4,-0.4),
arrow(-0.2,-0.4,-4,-0.4),locate(0.1,3.5,green(h))
)}}}
In all triangles the measures of the angles add up to {{{180^o}}} :
{{{A+B+C=180^o}}} .
In isosceles triangles in particular, the base angles have the same measure:
{{{A=C}}}
 
IF you have VERTICAL ANGLE {{{B}}} ,
{{{system(A+B+C=180^o,A=C)}}}-->{{{system(2A+B=180^o,A=C)}}}-->{{{system(2A=180^o-B,A=C)}}}-->{{{A=C=(180^o-B)/2}}} .
 
Otherwise, there are other equations that relate other measurements
(you would probably need 2) to the measure of the base angles.