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In the triangle $ABC$, $AB = 8$ cm, $AC = 7$ cm, \angle ABC = 0.5$ radians and \angle ACB = x$ radians - Edexcel - A-Level Maths Pure - Question 8 - 2005 - Paper 2

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In-the-triangle-$ABC$,-$AB-=-8$-cm,-$AC-=-7$-cm,-\angle-ABC-=-0.5$-radians-and-\angle-ACB-=-x$-radians-Edexcel-A-Level Maths Pure-Question 8-2005-Paper 2.png

In the triangle $ABC$, $AB = 8$ cm, $AC = 7$ cm, \angle ABC = 0.5$ radians and \angle ACB = x$ radians. (a) Use the sine rule to find the value of $sin x$, giving y... show full transcript

Worked Solution & Example Answer:In the triangle $ABC$, $AB = 8$ cm, $AC = 7$ cm, \angle ABC = 0.5$ radians and \angle ACB = x$ radians - Edexcel - A-Level Maths Pure - Question 8 - 2005 - Paper 2

Step 1

Use the sine rule to find the value of $sin x$

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Answer

Using the sine rule, we have:

ABsin(ACB)=ACsin(ABC)\frac{AB}{\sin(\angle ACB)} = \frac{AC}{\sin(\angle ABC)}

Substituting the known values:

8sinx=7sin(0.5)\frac{8}{\sin x} = \frac{7}{\sin(0.5)}

Calculating sin(0.5)\sin(0.5):

sin(0.5)0.4794\sin(0.5) \approx 0.4794

Thus, substituting into the equation gives:

8sinx=70.4794\frac{8}{\sin x} = \frac{7}{0.4794}

Cross multiplying:

80.4794=7sinx8 \cdot 0.4794 = 7 \cdot \sin x

So,

sinx=80.479470.548\sin x = \frac{8 \cdot 0.4794}{7} \approx 0.548

Rounding to 3 decimal places:

sinx0.548\sin x \approx 0.548

Step 2

find these values of $x$

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Answer

To find the values of xx, we take the inverse sine:

x=sin1(0.548)0.582 radiansx = \sin^{-1}(0.548) \approx 0.582 \text{ radians}

Since the sine function is positive in the first and second quadrants, we have:

For the second solution, we calculate:

x=πsin1(0.548)π0.5822.560 radiansx = \pi - \sin^{-1}(0.548) \approx \pi - 0.582 \approx 2.560 \text{ radians}

Thus, the two values of xx are:

  1. x0.58x \approx 0.58 radians (to 2 decimal places)
  2. x2.56x \approx 2.56 radians (to 2 decimal places)

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