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In the given figure, chord AB subtends an angle of `115^@` at the centre O of a circle of radius 20 cm. Calculate AB correct to nearest cm. |
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Answer» Let `D` is the mid point of `AB`. Please refer to video to see the diagram. Now, in `Delta OAD` and `Delta OBD`, `OA = OB`(radius) `OD = OD` `AD = DB` `:. Delta OAD ~= Delta OBD` `:. /_AOD = /_BOD = 115/2 = 57.5^@` Now, `AD = AOsin57.5^@ = 20sin57.5^@` We know, `sin 60^@ = sqrt3/2 ~=0.86` `:. sin57.5^@ ~= 0.8` So, `AD = 20**0.8 = 16cm` `:. AB = 2**AD = 2**16 = 32cm` |
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