The diagram shows a circle and an equilateral triangle - Edexcel - GCSE Maths - Question 14 - 2018 - Paper 2

Since one side of the equilateral triangle is the diameter of the circle, the diameter is twice the radius:

$d = 2r = 2 \times 7 \approx 14\,\text{cm}$

The area A of an equilateral triangle with side length s can be calculated using the formula:

$A = \frac{\sqrt{3}}{4} s^2$

Substituting the side length:

$A = \frac{\sqrt{3}}{4} (14)^2 = \frac{\sqrt{3}}{4} \times 196 \approx 84.87\,\text{cm}^2$

Rounding to 3 significant figures, the area of the triangle is:

$A \approx 85.0\,\text{cm}^2$