The diagram shows a triangle ABC,
AB is the shortest side - AQA - A-Level Maths Pure - Question 4 - 2022 - Paper 2
Question 4
The diagram shows a triangle ABC,
AB is the shortest side. The lengths of AC and BC are 6.1 cm and 8.7 cm respectively.
The size of angle ABC is 38°
Find the size... show full transcript
Worked Solution & Example Answer:The diagram shows a triangle ABC,
AB is the shortest side - AQA - A-Level Maths Pure - Question 4 - 2022 - Paper 2
Step 1
Use the Sine Rule
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Answer
To find the largest angle in triangle ABC, use the Sine Rule, which states:
sinAa=sinBb=sinCc
Let:
AC = 6.1 cm,
BC = 8.7 cm,
angle ABC = 38°.
We can denote:
AB = c,
angle A = C,
angle B = ABC, and
angle A = 180° - A - B.
Step 2
Substituting Values
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Answer
Substituting the known values into the sin rule yields:
sin(38°)c=sin(A)6.1=sin(180°−A−38°)8.7
Now, let’s find the length of side AB (c).
Calculating:
c=sin(A)8.7⋅sin(38°)
Step 3
Finding Angle A
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Answer
Using the Sine Rule again:
Calculating angle A gives:
A=arcsin(8.76.1⋅sin(38°))≈61° (rounded to the nearest degree)
Now, since angle A + angle B + angle C = 180°, we can identify the largest angle.
Step 4
Determine the Largest Angle
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