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If circumradius of triangle is 2, then t...

If circumradius of triangle is 2, then the maximum value of `(abc)/(a+b+c)` is

A

1

B

2

C

3

D

4

Text Solution

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The correct Answer is:
To find the maximum value of \(\frac{abc}{a+b+c}\) when the circumradius \(R\) of a triangle is 2, we can follow these steps: ### Step 1: Understanding the Circumradius The circumradius \(R\) of a triangle is related to its sides \(a\), \(b\), and \(c\) by the formula: \[ R = \frac{abc}{4K} \] where \(K\) is the area of the triangle. Given that \(R = 2\), we have: \[ 2 = \frac{abc}{4K} \implies abc = 8K \] ### Step 2: Using the Homogeneity of the Expression The expression \(\frac{abc}{a+b+c}\) is homogeneous of degree 0. This means that if we scale \(a\), \(b\), and \(c\) by a factor \(k\), the value of the expression remains unchanged. Therefore, we can assume that the triangle is equilateral to maximize the expression. ### Step 3: Finding the Side Length of the Equilateral Triangle For an equilateral triangle with circumradius \(R = 2\), the side length \(s\) can be calculated using the relation: \[ R = \frac{s}{\sqrt{3}} \] Thus, we have: \[ 2 = \frac{s}{\sqrt{3}} \implies s = 2\sqrt{3} \] ### Step 4: Assigning Values to \(a\), \(b\), and \(c\) Since the triangle is equilateral, we have: \[ a = b = c = 2\sqrt{3} \] ### Step 5: Calculating the Expression Now we can substitute \(a\), \(b\), and \(c\) into the expression \(\frac{abc}{a+b+c}\): \[ abc = (2\sqrt{3})(2\sqrt{3})(2\sqrt{3}) = 8 \cdot 3 = 24 \] \[ a + b + c = 2\sqrt{3} + 2\sqrt{3} + 2\sqrt{3} = 6\sqrt{3} \] Thus, we have: \[ \frac{abc}{a+b+c} = \frac{24}{6\sqrt{3}} = \frac{4}{\sqrt{3}} \cdot \sqrt{3} = 4 \] ### Conclusion The maximum value of \(\frac{abc}{a+b+c}\) when the circumradius of the triangle is 2 is: \[ \boxed{4} \]

To find the maximum value of \(\frac{abc}{a+b+c}\) when the circumradius \(R\) of a triangle is 2, we can follow these steps: ### Step 1: Understanding the Circumradius The circumradius \(R\) of a triangle is related to its sides \(a\), \(b\), and \(c\) by the formula: \[ R = \frac{abc}{4K} \] where \(K\) is the area of the triangle. Given that \(R = 2\), we have: ...
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