A jeweler is making a fitting for a pyramid-shaped gem and needs to know the perpendicular height of the pyramid. Both the slant height and the lengths of the sides of the square base are 2 cm. Find the perpendicular height of the pyramid. Round to the nearest tenth.(1 point)

Responses

3 cm
3 cm

1 cm
1 cm

2.2 cm
2.2 cm

1.7 cm

1 answer

To find the perpendicular height \( h \) of the pyramid, we can use the Pythagorean theorem.

  1. First, we know that the base of the pyramid is a square with each side measuring \( 2 \) cm.
  2. The slant height \( l \) of the pyramid is given as \( 2 \) cm.
  3. The height of the pyramid \( h \) is perpendicular to the center of the base and meets at the vertex of the pyramid.

To find the height \( h \), we first need to calculate half the length of the base’s diagonal, which serves as one leg of a right triangle where:

  • \( l \) (slant height) is the hypotenuse,
  • \( h \) is one leg (height),
  • half the length of the diagonal of the square base is the other leg.
  1. The diagonal \( d \) of a square with side length \( s \) is given by: \[ d = s\sqrt{2} \] For our base, \( s = 2 \) cm: \[ d = 2\sqrt{2} \]

  2. Half the diagonal \( \frac{d}{2} = \frac{2\sqrt{2}}{2} = \sqrt{2} \) cm.

  3. We now apply the Pythagorean theorem: \[ l^2 = h^2 + \left(\frac{d}{2}\right)^2 \] Plugging in the values: \[ 2^2 = h^2 + (\sqrt{2})^2 \] Which simplifies to: \[ 4 = h^2 + 2 \] \[ h^2 = 4 - 2 \] \[ h^2 = 2 \] \[ h = \sqrt{2} \approx 1.414 \]

  4. Rounding \( h \) to the nearest tenth gives us \( 1.4 \) cm, but the closest answer choice provided is \( 1 \) cm.

So the nearest answer choice given is 1 cm.