A triangle of area 1 has sides of lengths a.b. and c where a ≥ b ≥ c. Prove that b ≥ √2. Whoever gives the fastest and the most reasonable answer will get marked brainliest.
We can use the area formula for a triangle in terms of its side lengths, known as Heron's formula, to solve this problem. Let s = (a + b + c)/2 be the semiperimeter of the triangle, then the area of the triangle is given by:
Since b ≥ c, we have b-c ≥ 0. Therefore, the only way for this inequality to hold is if a+b+c ≥ 2√2. Since the area of the triangle is fixed at 1, we have:
Answers & Comments
Step-by-step explanation:
We can use the area formula for a triangle in terms of its side lengths, known as Heron's formula, to solve this problem. Let s = (a + b + c)/2 be the semiperimeter of the triangle, then the area of the triangle is given by:
A = √(s(s-a)(s-b)(s-c))
Since A = 1, we have:
1 = √(s(s-a)(s-b)(s-c))
Squaring both sides, we get:
s(s-a)(s-b)(s-c) = 1
Expanding the product, we get:
s^4 - (a+b+c)s^3 + (ab+bc+ca)s^2 - abc(s) = 1
Since s = (a+b+c)/2, we can substitute to get:
[(a+b+c)/2]^4 - (a+b+c)^3/2 + (ab+bc+ca)(a+b+c)^2/4 - abc(a+b+c)/2 - 1 = 0
Simplifying and factoring out (a+b+c), we get:
(a+b+c)[(a+b+c)^3/16 - (a+b+c)/2 + (ab+bc+ca)/4 - abc/2 - 1/(a+b+c)] = 0
Since a, b, c are positive, we have a+b+c > 0. Therefore, the second factor must be equal to zero:
(a+b+c)^3/16 - (a+b+c)/2 + (ab+bc+ca)/4 - abc/2 - 1/(a+b+c) = 0
Multiplying both sides by 16(a+b+c), we get:
(a+b+c)^4 - 8(a+b+c)^2 + 16(ab+bc+ca)(a+b+c) - 32abc(a+b+c) - 16 = 0
We can use the fact that a ≥ b ≥ c to simplify this expression. Since (a-b)(a-c) ≥ 0, we have:
ab + ac ≥ b^2 + bc
2(ab + ac) ≥ b^2 + 2bc
Substituting this inequality into the previous expression, we get:
(a+b+c)^4 - 8(a+b+c)^2 + 2(b^2+2bc+c^2)(a+b+c) - 32abc(a+b+c) - 16 ≤ 0
Simplifying and factoring, we get:
(b-c)^2(a+b+c-2√2)(a+b+c+2√2) ≤ 0
Since b ≥ c, we have b-c ≥ 0. Therefore, the only way for this inequality to hold is if a+b+c ≥ 2√2. Since the area of the triangle is fixed at 1, we have:
1 = √(s(s-a)(s-b)(s-c)) ≤ √(s(s-c)^3) = √[(a+b+c)(a+b-c)(a+c-b)(b+c-a)] ≤ √[(a+b+c)(a+b+c-2b)(a+b+c-2c)(a+b+c-2a)]
= √[(a+b+c)(a+b+c-4b)(a+b+c-4c)(a+b+c-4a)]
= √[(a+b+c)(3a-3b+c)(3a+3b-5c)(-3a+b+3c)]
Since a, b, c are positive, we have a+b+c > 0. Therefore, the only way for this inequality to hold is if b ≥
mark me brillent