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Find the distance x in the diagram below (not to scale) - Leaving Cert Mathematics - Question 6 - 2017

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Find the distance x in the diagram below (not to scale). Give your answer correct to 2 decimal places. Find the distance y in the diagram below (not to scale). Give... show full transcript

Worked Solution & Example Answer:Find the distance x in the diagram below (not to scale) - Leaving Cert Mathematics - Question 6 - 2017

Step 1

Find the distance x in the diagram below (not to scale).

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Answer

To find the distance xx, we can use the sine rule. According to the sine rule:

xsin(63)=10sin(65)\frac{x}{\sin(63^\circ)} = \frac{10}{\sin(65^\circ)}

Rearranging this formula:

x=10sin(63)sin(65)x = \frac{10 \cdot \sin(63^\circ)}{\sin(65^\circ)}

Now, using a calculator, we get:

  1. Calculate sin(63)0.8910\sin(63^\circ) \approx 0.8910.
  2. Calculate sin(65)0.9063\sin(65^\circ) \approx 0.9063.
  3. Substitute into the equation:

x=100.89100.90638.84 cmx = \frac{10 \cdot 0.8910}{0.9063} \approx 8.84 \text{ cm}

Thus, the distance x is approximately 8.84 cm.

Step 2

Find the distance y in the diagram below (not to scale).

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Answer

To calculate the distance yy, we can again apply the cosine rule:

y2=a2+b22abcos(C)y^2 = a^2 + b^2 - 2ab \cdot \cos(C)

Where:

  • a=8.5a = 8.5 cm
  • b=10.2b = 10.2 cm
  • C=53.8C = 53.8^\circ

Thus:

y2=(8.5)2+(10.2)22(8.5)(10.2)cos(53.8)y^2 = (8.5)^2 + (10.2)^2 - 2 \cdot (8.5) \cdot (10.2) \cdot \cos(53.8^\circ)

Calculating each term:

  1. y2=72.25+104.0428.510.20.5736y^2 = 72.25 + 104.04 - 2 \cdot 8.5 \cdot 10.2 \cdot 0.5736.
  2. Then, plug in the values: y2=72.25+104.0484.0492.25y^2 = 72.25 + 104.04 - 84.04 \approx 92.25
  3. Finally, take the square root: y92.259.61 cmy \approx \sqrt{92.25} \approx 9.61 \text{ cm}

Therefore, the distance y is approximately 9.61 cm.

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