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In a window frame the woodframe has inside dimensions FG = 80 cm and HF = 136 cm. Calculate the length of the arc HI, if the centre of the circle of the arc is the midpoint of FG

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Answer: 26.18 cm

Explanation:

To calculate the length of the arc HI, you need to find the radius of the circle (since the center of the circle is the midpoint of FG) and then use the formula for the length of an arc.

Given:

FG = 80 cm

HF = 136 cm

The radius of the circle is the average of FG and HF because the center is the midpoint of FG:

Radius (r) = (FG + HF) / 2

Radius (r) = (80 cm + 136 cm) / 2

Radius (r) = 216 cm / 2

Radius (r) = 108 cm

Now that we have the radius, you can calculate the length of the arc HI using the formula:

Arc Length (L) = (θ/360) * (2πr)

First, you need to find the angle θ at the center of the circle formed by arc HI. To do this, you can use the properties of similar triangles since FH is a chord of the circle and HI is an arc of the same circle.

You have:

HF (chord length) = 136 cm

FG (chord length) = 80 cm

Let's call θ the angle at the center of the circle (the angle HI makes at the center of the circle). Using similar triangles:

(sin(θ/2)) = (opposite side) / (hypotenuse)

(sin(θ/2)) = (80 cm / 2) / 108 cm

(sin(θ/2)) = 40 cm / 108 cm

(sin(θ/2)) ≈ 0.3704

Now, you can find θ by taking the arcsin of 0.3704:

θ/2 ≈ arcsin(0.3704)

θ/2 ≈ 21.84 degrees

Now, double θ/2 to find θ:

θ ≈ 2 * 21.84 degrees

θ ≈ 43.68 degrees

Now that you have θ and the radius (r), you can calculate the arc length (L):

Arc Length (HI) = (θ/360) * (2πr)

Arc Length (HI) = (43.68/360) * (2π * 108 cm)

Arc Length (HI) ≈ (0.121) * (216π cm)

Arc Length (HI) ≈ 26.18 cm (rounded to two decimal places)

So, the length of the arc HI is approximately 26.18 cm.

User Shikarishambu
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