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| 1. |
Anequilateral triangle of side 9 cm is inscribed in a circle. Find the radiusof the circle. |
| Answer» let the equilateral triangle be ABC of each side of 9 cm prescribed in a circle.draw a perpendicular from A to BC , from C to AB, from B to AC respectively.now name the intersection point of perpendicular from A to BC as D,So, BD will be = `9/2` = 4.5let point of intersection of all perpendicular to centre of the circle as O.Now as we know that `/_OBD= 60^@` and `/_ODB=90^@`So, `/_DOB=180^@ - 60^@ - 90^@` = `30^@`now, `Cos 30^@` = `BD/BO``sqrt 3/ 2 = 4.5/BO`BO= `3*sqrt 3 ` | |