Examples with solutions for Circumference: Using Pythagoras' theorem

Exercise #1

Look at the triangle and circle below.

Which has the larger perimeter/circumference?

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Video Solution

Step-by-Step Solution

To determine which has the larger measurement, the triangle's perimeter or the circle's circumference, we need to compute both values.

Step 1: Calculate the perimeter of the Triangle
We are given two sides of the triangle: 6 and 5. Since it's implied to be a right triangle, we apply the Pythagorean theorem to find the third side, the hypotenuse c c :

c=62+52=36+25=61 c = \sqrt{6^2 + 5^2} = \sqrt{36 + 25} = \sqrt{61}

The perimeter P P of the triangle is:

P=6+5+6111+7.81=18.81 P = 6 + 5 + \sqrt{61} \approx 11 + 7.81 = 18.81

Step 2: Calculate the circumference of the Circle
The circumference C C of a circle with radius r r is given by the formula:

C=2πr C = 2 \pi r

Assuming the radius of the circle is equivalent to the '6' mentioned for the green line in the SVG:

C=2π×637.7 C = 2 \pi \times 6 \approx 37.7

Step 3: Compare the Triangle's Perimeter and the Circle's Circumference
We compare the values:

  • Perimeter of the Triangle: P18.81 P \approx 18.81
  • Circumference of the Circle: C37.7 C \approx 37.7

The circumference of the circle (37.7) is greater than the perimeter of the triangle (18.81).

Therefore, the circle has the larger measurement.

Conclusion: The circle has the larger perimeter.

Answer

The circle

Exercise #2

A square with sides measuring √2 is drawn inside a circle.
What is the circumference of the circle?

Video Solution

Answer

2π 2\pi

Exercise #3

Triangle ABC given in the drawing is isosceles, AB=AC

AD is perpendicular to BC

The circle whose diameter is AC is 13π 13\pi cm

For side DC, a semicircle whose area is AAABBBCCCDDD cm² is placed

What is the area of the triangle?

Video Solution

Answer

60 cm²