The area of the largest triangle that can be inscribed in a semi-circle of radius 6 cm is:
- AOption (a)
36 cm²
- BOption (b)
72 cm²
- COption (c)
38 cm²
- DOption (d)
76 cm²
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Correct answer
36 cm²
Why this answer is correct
Shortcut Trick
The area of the largest triangle that can be inscribed in a semi-circle of radius r is always r2.
Given radius (r) = 6 cm
⇒ Area = 62
⇒ Area = 36 cm2
∴ The correct answer is 36 cm2.
Alternate Method
Given:
Radius of the semi-circle (r) = 6 cm
Formula Used:
Area of a triangle = 1/2 × Base × Height
For a triangle inscribed in a semi-circle to have the maximum area, its base must be the diameter of the semi-circle and its height must be equal to the radius.
⇒ Base of triangle (b) = Diameter of semi-circle = 2 × r
⇒ Base (b) = 2 × 6 = 12 cm
⇒ Maximum Height (h) = Radius of semi-circle = 6 cm
⇒ Maximum Area = 1/2 × Base × Height
⇒ Area = 1/2 × 12 × 6
⇒ Area = 6 × 6
⇒ Area = 36 cm2
∴ The correct answer is 36 cm2.
Additional Information
Angle in a Semi-circle
Any triangle inscribed in a semi-circle with the diameter as one of its sides is always a right-angled triangle (Angle = 90°).
Area and Perimeter of Semi-circle
Area = 1/2 × πr2 and Perimeter = πr + 2r (where 2r is the diameter).
Maximum Area of Inscribed Rectangle
The largest rectangle that can be inscribed in a semi-circle of radius r has an area of r2.