Q.

The base of an isosceles triangle is 10 cm and one of its equal sides is 13 cm. Find its area using Heron’s formula.


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a

60 cm2

b

80 cm2

c

50 cm2

d

90 cm2 

answer is A.

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Detailed Solution

Concept- We'll calculate the triangle's semi-perimeter as well as the distance between each side and the semi-perimeter. These values will be used as replacements in Heron's formula. After that, we'll figure out the area and solve the phrase.
formulas employed
The following formulas will be applied:
1) A triangle's semi-perimeter is equal to half of the sum of its side lengths:
s=a+b+c2
2) The area of a triangle with sides a, b, and c and a semi-perimeter s is given by the Heron's formula: A=s(s-a)(s-b)(s-c).
We are aware that an isosceles triangle has two equal sides. Given that one of the equal sides is 13 cm long, the other equal side must also be 13 cm long.
We will start by determining the triangle's semiperimeter. In the semi-perimeter formula, we will change a and b and c to 10 and 13, respectively. As a result, we have
s=10+13+132
s=362
s=18.
We shall now calculate the value of s-a. When we substitute 10 for a and 18 for s, the result is 18-10=8.
-We'll determine the value of s-b. We obtain 18-13=5 by substituting 13 for b and 18 for s.
We'll determine the value of s-c. 13 for c and 18 for s in the formula
we obtain ⇒18−13=5
We shall now calculate the triangle's area.—The Heron's formula, A=s(s-a)(s-b)(s-c), can be changed to read A=8×8×5×5 by substituting 18 for s, 8 for s-a, and 5 for s-and s-c.
The numbers will be expressed as the sum of their prime factors. As a result, we have A=2×3×3×2×2×2×5×5.
The phrases will be rearranged, the same numbers will be grouped, and the terms that appear in pairs will be removed from the square root: A=2×2×2×2×2×3×3×5×5.
A=2×2×3×5
When we multiply the terms, we obtain "A=60." The triangle has a surface area of 60 square centimetres.
Hence, option 1 is correct.
 
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