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Séan is making an access ramp for a building - Junior Cycle Mathematics - Question 11 - 2016

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Question 11

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Séan is making an access ramp for a building. The ramp is in the shape of a right-angled triangle. A diagram of the ramp is shown below. The lengths of two of the si... show full transcript

Worked Solution & Example Answer:Séan is making an access ramp for a building - Junior Cycle Mathematics - Question 11 - 2016

Step 1

Write down the length of the side adjacent to the angle A.

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Answer

The side adjacent to angle A is calculated using the properties of the right-angled triangle. Given that the opposite side is 20 cm and the hypotenuse is 260 cm, we can apply the cosine function:

extAdjacent=extHypotenuseimesextcos(A) ext{Adjacent} = ext{Hypotenuse} imes ext{cos}(A)

However, using Pythagorean theorem as a direct method for calculation, we have: extAdjacent=2602202=67600400=67200=260 ext{Adjacent} = \sqrt{260^2 - 20^2} = \sqrt{67600 - 400} = \sqrt{67200} = 260 cm.

Step 2

Write down the value of tan A as a fraction.

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Answer

The tangent function is defined as the ratio of the opposite side to the adjacent side. Thus:

tan(A)=OppositeAdjacent=20260=113\tan(A) = \frac{\text{Opposite}}{\text{Adjacent}} = \frac{20}{260} = \frac{1}{13}.

Step 3

Use your answer to part (a)(ii) to find the size of the angle A.

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Answer

To find the angle A, we can use the inverse tangent function:

A=tan1(113)4.43°A = \tan^{-1}\left(\frac{1}{13}\right) \approx 4.43°

Therefore, rounding to the nearest degree, the angle A is:

A4°A \approx 4°.

Step 4

Is Séan’s ramp acceptable? (Tick (✔) one box only.)

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Answer

Yes

Reason: The angle A (4°) is less than the acceptable maximum angle (5°). Therefore, the ramp is acceptable.

Step 5

Use the Theorem of Pythagoras to find the value of x.

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Answer

Using the Theorem of Pythagoras, the relationship between the sides is given by:

x2+2242=2262x^2 + 224^2 = 226^2

Calculating each side: x2+50176=51076x^2 + 50176 = 51076

Therefore, x2=5107650176=900x^2 = 51076 - 50176 = 900

Taking the square root gives: x=900=30x = \sqrt{900} = 30 cm.

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