Practicing Success
ABCD is cyclic quadrilateral. Sides AB and DC, when produced, meet at E, and sides BC and AD, when produced, meet at F. If $\angle$BFA = $60^\circ$ and $\angle$AED = $30^\circ$, then the measure of $\angle$ABC is: |
65° 70° 80° 75° |
75° |
In triangle ABF \(\alpha \) + \(\theta \) + 60 = 180 = \(\alpha \) + \(\theta \) = 120 ..(1) In triangle ADE \(\alpha \) + \(\pi \) - \(\theta \) + 30 = 180 = \(\alpha \) - \(\theta \) + 30 = 0 ..(2) From eq(1) and (2), we have \(\alpha \) = 45 and \(\theta \) = 75 Therefore, \(\angle\)ABC = \({75}^\circ\). |