Quantitative Aptitude Ques 1469
Question: ABCD is a cyclic quadrilateral and AD is a diameter. If $ \angle DAC=55{}^\circ , $ then the value of $ \angle ABC $ is
Options:
A) $ 55{}^\circ $
B) $ 35{}^\circ $
C) $ 145{}^\circ $
D) $ 125{}^\circ $
Show Answer
Answer:
Correct Answer: C
Solution:
- In $ \Delta ACD, $ $ \angle DAC=55{}^\circ $ [given]
$ \angle ACD=90{}^\circ = $ Angle in a semi-circle
$ \angle ADC=180{}^\circ -90{}^\circ -55{}^\circ $
$ =180{}^\circ -145{}^\circ =35{}^\circ $
Now, in a cyclic quadrilateral sum of opposite angles $ =180{}^\circ $
$ \angle ABC+\angle ADC=180{}^\circ $
$ \angle ABC=180{}^\circ -\angle ADC=180{}^\circ -35{}^\circ =145{}^\circ $