MCQ
In the given figure, $\angle\text{AOB}=90^\circ$ and $\angle\text{ABC}=30^\circ.$ Then, $\angle\text{CAO}=?$
  • A
    $45^\circ$
  • B
    $90^\circ$
  • C
    $30^\circ$
  • $60^\circ$

Answer

Correct option: D.
$60^\circ$

We have:
$\angle\text{AOB}=2\angle\text{ACB}$
$\Rightarrow\angle\text{ACB}=\frac{1}{2}\angle\text{AOB}=(\frac{1}{2}\times90^\circ)=45^\circ$
$\Rightarrow\angle\text{ACB}=45^\circ$
$\angle\text{COA}=2\angle\text{CBA}=(2\times30^\circ)=60^\circ$
$\therefore\angle\text{COD}=180^\circ-\angle\text{COA}=(180^\circ-60^\circ)=120^\circ$
$\Rightarrow\angle\text{CAO}=\frac{1}{2}\angle\text{COD}=(\frac{1}{2}\times120^\circ)=60^\circ$
$\Rightarrow\angle\text{CAO}=60^\circ$

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