Question

Q21. Construct ZABC = 80°using a protractor and bisect it using a ruler and a
compass. Write the measure of the bisected angles.
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Answer 1

Answer:

120

Step-by-step explanation:

1. Draw a ray OA. 

2. With the help of a protractor , construction ∠ BOA = 80∘ 

3. Taking O as center and any suitable radius , draw an arc to intersect rays OA and OB at points P and Q respectively . 

4. Take radius more than half the radius OP.With this radius make an arc from point P and Q which will intersect at X . By joining O and X we get bisector of ∠AOB . 

Let ray OC be the bisector of ∠ BOA , then ∠ COA = 21∠ BOA = 21×80∘=40∘ . 

5. With Q as center and radius equal to PQ , draw an arc to cut the extended arc PQ at R . Join OR and produce it to form ray OD , then ∠ DOA = 2∠ BOA = 2×80∘=160∘.

6. Bisect ∠ DOB as done in step 4. Let OE be the bisector of ∠ DOB is then 

∠ EOA = ∠ EOB + ∠ BOA = 21∠ DOB + ∠ BOA = 21(80)∘+80∘=40∘+80∘=120∘