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# Triangles: Isosceles

If \$\$AD=DB\$\$ and \$\$DC=BC\$\$ as shown above, what is the value of \$\$xº\$\$?
Correct. [[snippet]] Given that \$\$AD = DB\$\$, \$\$\angle DAB = \angle DBA = 40º\$\$. Since the sum of all angles in a triangle is \$\$180º\$\$, > \$\$ADB = 180º - 2(40º) = 180º - 80º = 100º\$\$. Based on this, angle \$\$BDC\$\$, the supplementary angle of \$\$ADB\$\$, is \$\$180º - 100º = 80º\$\$. Hence > \$\$xº = 180º - 2(80º) = 180º - 160º = 20º\$\$.
Incorrect. [[snippet]]
Incorrect. [[snippet]]
Incorrect. [[snippet]]
Incorrect. [[snippet]]
\$\$20º\$\$
\$\$40º\$\$
\$\$60º\$\$
\$\$80º\$\$
\$\$100º\$\$