Construct a right-angled triangle ABC, where:
|AB| = 6 cm
|ABC| = 90º
|AC| = 10 cm
(ii) On your diagram, measure the angle ∠CAB - Junior Cycle Mathematics - Question i - 2014
Question i
Construct a right-angled triangle ABC, where:
|AB| = 6 cm
|ABC| = 90º
|AC| = 10 cm
(ii) On your diagram, measure the angle ∠CAB. Give your answer correct to the ne... show full transcript
Worked Solution & Example Answer:Construct a right-angled triangle ABC, where:
|AB| = 6 cm
|ABC| = 90º
|AC| = 10 cm
(ii) On your diagram, measure the angle ∠CAB - Junior Cycle Mathematics - Question i - 2014
Step 1
On your diagram, measure the angle ∠CAB. Give your answer correct to the nearest degree.
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Answer
Using a protractor, the angle ∠CAB is measured to be 53º.
Step 2
Let X be the whole number you wrote as your answer to (ii).
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Answer
Here, X = 53.
Step 3
Use a calculator to find cos X. Give your answer correct to 3 decimal places.
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Answer
Using a calculator, we find:
cos(53º)≈0.6018≈0.602
Thus, the answer is 0.602.
Step 4
Explain why your answer in (iii) is not the same as Jacinta’s.
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Answer
Jacinta assumes that cos(∠CAB) is exactly 0.6. However, since cos(53º) is approximately 0.602, it cannot be exactly 0.6. Also, since X is a whole number, cos(X) can only take specific values, and as such it will never equal 0.6 exactly.
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