A correct drawing of a 30-60-90 triangle.
<a href="//commons.wikimedia.org/wiki/User:Incnis_Mrsi" title="User:Incnis Mrsi">Incnis Mrsi</a>
<span class="int-own-work" lang="en">Own work</span>, parts of <a href="//commons.wikimedia.org/wiki/File:Equilateral-triangle.svg" title="File:Equilateral-triangle.svg">File: Equilateral-triangle.svg</a> were reused