Question

A spiral staircase turns $270^\circ$ as it rises 10 feet. The radius of the staircase is 3 feet. What is the number of feet in the length of the handrail

Answer 1

The number of feet in the length of the handrail is 17.3 ft.

The easiest way to see this is to imagine that we can "unfold" the spiral to create a rectangle

The bottom side of the rectangle is just the arc length of a circle with a radius of 3 ft  turned through 270°= (3/4) of a whole revolution

(3/4) (2pi) (3)  =  (9/2)pi ft =   4.5 pi ft

The side of the rectangle will be the rise of the staircase = 10ft

And the diagonal of the rectangle will be the length of the handrail

We can use the Pythagorean Theorem to solve this

Handrail length = √ [ (4.5 pi)^2 + 10^2 ]  ≈  17.3 ft

Pythagorean theorem is the well-known geometric theorem that the sum of the squares on the legs of a right triangle is equal to the square on the hypotenuse.

Learn more about the Pythagorean theorem here: brainly.com/question/343682

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