MathDB
Triangle With Angles

Source:

February 15, 2009
exterior angle

Problem Statement

In the figure \overline{AB} \equal{} \overline{AC}, angle BAD \equal{} 30^{\circ}, and \overline{AE} \equal{} \overline{AD}. [asy]unitsize(20); defaultpen(linewidth(.8pt)+fontsize(8pt)); pair A=(3,3),B=(0,0),C=(6,0),D=(2,0),E=(5,1); draw(A--B--C--cycle); draw(A--D--E); label("AA",A,N); label("BB",B,W); label("CC",C,E); label("DD",D,S); label("EE",E,NE);[/asy]Then angle CDE CDE equals: <spanclass=latexbold>(A)</span> 712<spanclass=latexbold>(B)</span> 10<spanclass=latexbold>(C)</span> 1212<spanclass=latexbold>(D)</span> 15<spanclass=latexbold>(E)</span> 20 <span class='latex-bold'>(A)</span>\ 7\frac {1}{2}^{\circ} \qquad<span class='latex-bold'>(B)</span>\ 10^{\circ} \qquad<span class='latex-bold'>(C)</span>\ 12\frac {1}{2}^{\circ} \qquad<span class='latex-bold'>(D)</span>\ 15^{\circ} \qquad<span class='latex-bold'>(E)</span>\ 20^{\circ}