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Séan makes a clinometer using a protractor, a straw, a piece of thread and a piece of plasticine (used as a weight) - Junior Cycle Mathematics - Question 13 - 2012

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Question 13

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Séan makes a clinometer using a protractor, a straw, a piece of thread and a piece of plasticine (used as a weight). He stands 10 m from a tree and uses his clinomet... show full transcript

Worked Solution & Example Answer:Séan makes a clinometer using a protractor, a straw, a piece of thread and a piece of plasticine (used as a weight) - Junior Cycle Mathematics - Question 13 - 2012

Step 1

Find the angle of elevation by reading the clinometer above.

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Answer

The angle of elevation read from the clinometer is given as 65°.

Step 2

Calculate the height h as shown in the diagram. Give your answer correct to two decimal places.

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Answer

Using the tangent function:

tan(65°)=h10\tan(65°) = \frac{h}{10}

We know that:

h=10×tan(65°)h = 10 \times \tan(65°)

Calculating: h=10×2.1445h = 10 \times 2.1445 gives h=21.445 mh = 21.445 \text{ m}

Rounding to two decimal places, we get

h = 21.45 m.

Step 3

Find the total height of the tree.

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Answer

The total height of the tree is calculated by adding Séan's height to the height calculated:

Total height=h+extSeˊansheight=21.45+1.75\text{Total height} = h + ext{Séan's height} = 21.45 + 1.75

Thus, the total height of the tree is

23.20 m.

Step 4

Another student uses the same method as Séan and finds the height of the tree to be 23.1 m. Séan did not get this answer. Give one possible reason why the answers might be different.

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Answer

One possible reason for the difference in height could be that the other student measured the angle of elevation differently, perhaps reading 64° instead of 65°. Small variations in angle can lead to significant differences in height calculations due to the tangent function’s sensitivity.

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