A) \[{{20}^{{}^\circ }}\]
B) \[{{10}^{{}^\circ }}\]
C) \[{{30}^{{}^\circ }}\]
D) \[{{25}^{{}^\circ }}\]
Correct Answer: B
Solution :
(b): In \[\Delta OAB\], we have: \[\angle OAB+\angle OBA+\angle AOB={{180}^{{}^\circ }}\] \[\therefore \]\[{{45}^{{}^\circ }}+{{65}^{{}^\circ }}+\angle AOB={{180}^{{}^\circ }}\Rightarrow \angle AOB={{70}^{{}^\circ }}\] \[\therefore \]\[\angle COD=\angle AOB={{70}^{{}^\circ }}\] In \[\Delta OCD\], we have: \[\angle COD+\angle OCD+\angle ODC={{180}^{{}^\circ }}\] \[{{70}^{{}^\circ }}+{{100}^{{}^\circ }}+\angle ODC={{180}^{{}^\circ }}\Rightarrow \angle ODC={{10}^{{}^\circ }}\]You need to login to perform this action.
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