Comprehension

Consider the following for the three (03) items that follow: The sides of a triangle ABC are AB=3cm, BC=5cm and CA=7cm.

What is the area of the triangle?

This question was previously asked in
NDA-I (Mathematics) Official Paper (Held On: 13 Apr, 2025)
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  1. \(15\sqrt{13}/4\) square cm
  2. \(15\sqrt{13}/2\) square cm
  3. \(15\sqrt{13}\) square cm
  4. \(30\sqrt{13}\) square cm

Answer (Detailed Solution Below)

Option 1 : \(15\sqrt{13}/4\) square cm
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Detailed Solution

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Calculation:

Given,

The sides of the triangle are: a = 5 cm, c = 3 cm, and the angle B = \(120^\circ \) between sides a and c.

The area of the triangle is given by the formula:

\( \text{Area} = \frac{1}{2} \times a \times c \times \sin B \)

\( \text{Area} = \frac{1}{2} \times 5 \times 3 \times \sin(120^\circ) \)

We know that\(\sin(120^\circ) = \frac{\sqrt{3}}{2} \), so:

\( \text{Area} = \frac{1}{2} \times 5 \times 3 \times \frac{\sqrt{3}}{2} \)

\( \text{Area} = \frac{1}{2} \times 15 \times \frac{\sqrt{3}}{2} = \frac{15 \times \sqrt{3}}{4} \)

∴ The area of the triangle is \(\frac{15\sqrt{3}}{4} \) square cm.

Hence, the Correct answer is Option 1.

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