Niech [tex]\alpha=\measuredangle BAC[/tex], wówczas:
[tex]\measuredangle CAD=2\alpha\\\measuredangle DAE=4\alpha\\\measuredangle EAB=8\alpha[/tex]
Razem muszą tworzyć kąt pełny ([tex]360^\circ[/tex]), zatem:
[tex]\alpha+2\alpha+4\alpha+8\alpha=360^\circ\\15\alpha=360^\circ\\\alpha=24^\circ\\\measuredangle CAD=2\alpha=2*24^\circ=42^\circ[/tex]
