Mathematics
Grade9
Easy

Question

Find the length of the leg. Leave your answer in simplest radical form.

  1. 128
  2. 8√2
  3. 16
  4. 2√2

hintHint:

We are given a right-angled triangle. One angle is 45°, so remaining angle will be 45°. It is 45°-45°-90° triangle. We are given the length of the hypotenuse. We are asked to find the value of one of its leg. We have to use the properties of both right-angled triangle and 45°-45°-90° triangle.

The correct answer is: 8√2


    Let the given triangle be ABC
    ∠ABC = 90°
    Let the value of its leg be “p”.
    AB = p
    AC = 16
    It is a 45°-45°-90° triangle. The two angles of the triangle are same. It means the sides opposite to the triangle are equal. When a triangle has two sides equal, it is an isosceles triangle.
    The given triangle is an isosceles triangle.
    AB = BC
    So, BC = p
    Now, we will use the Pythagoras theorem. It states that, the square of the hypotenuse is equal to the sum of the square of the two sides.
    AC2 = AB2 + BC2
    162 = p2 + p2
    256 = 2p2
    Rearranging we get,
    2p2 = 256
    Dividing both the sides by 2 we get,
    p2 = 128
    p2 = 2 × 64
    Taking the square root we get
    p = 8√2
    Therefore, the value of one of its leg is 8√2.

    For such questions, we should know properties of different triangles.

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