MCQ
In the given figure, $AB \I CD$. If $\angle\text{AOC}=30^\circ$ and $\angle\text{OAB}=100^\circ.$ then $\angle\text{OCD}=?$ 
- ✓$80^\circ$
- B$100^\circ$
- C$130^\circ$
- D$150^\circ$
✓
Answer
Correct option: A.
$80^\circ$
Extend line $CD$ which intersect $AO$ at $M.$
(Corresponding angle)
$\angle\text{MOC}+\angle\text{CMO}=\angle\text{DCO}$ (exterior angle is equal to the sum of two opposite interior angles)
$\angle\text{DCO}=100^\circ+30^\circ=130^\circ$
(Corresponding angle)
$\angle\text{MOC}+\angle\text{CMO}=\angle\text{DCO}$ (exterior angle is equal to the sum of two opposite interior angles)
$\angle\text{DCO}=100^\circ+30^\circ=130^\circ$
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