Question
ΔABC is an equilateral triangle of side 14 cm. A semi circle on BC as diameter is drawn to meet AB at D, and AC at E. Find the area of the shaded region?
Answer: Option B
:
B
Option (b)
O is the centre of the circle and the mid-point of BC. DO is parallel to AC. So, ∠DOB = 60°
Area of Δ BDO =34 * 49
Area of sector OBD = 496
Hence area of the shaded region
= 2[496 – 34*49]
= 49[13 – 32]
Shortcut
By graphical division, there are 3 equilateral triangles of areas of √34 * 49
Area of interest = (area of semi circle [r22] - area of three triangles) = (49*12- 3*3*494)*(23) = 49*(13 – 32)
Was this answer helpful ?
:
B
Option (b)
O is the centre of the circle and the mid-point of BC. DO is parallel to AC. So, ∠DOB = 60°
Area of Δ BDO =34 * 49
Area of sector OBD = 496
Hence area of the shaded region
= 2[496 – 34*49]
= 49[13 – 32]
Shortcut
By graphical division, there are 3 equilateral triangles of areas of √34 * 49
Area of interest = (area of semi circle [r22] - area of three triangles) = (49*12- 3*3*494)*(23) = 49*(13 – 32)
Was this answer helpful ?
Submit Solution