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secondary 3 | A Maths
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Date Posted: 2 years ago
Views: 161
Use cosine rule to find ∠A and do the same to find ∠B.
Cosine rule :
① c² = a² + b² - 2ab cos ∠C
Or
② cos ∠C = (a² + b² - c²) / 2ab
Then 180° - ∠A - ∠B = ∠C (Angle sum of triangle)
You can just take a to be 2 units, b to be 3 units and c to be 4 units.
Alternatively,
Use variant ② of cosine rule :
② cos ∠C = (a² + b² - c²) / 2ab
then ∠C = cos-¹ [(a² + b² - c²) / 2ab]
sin ∠C = sin (cos-¹ [(a² + b² - c²) / 2ab])
Cosine rule :
① c² = a² + b² - 2ab cos ∠C
Or
② cos ∠C = (a² + b² - c²) / 2ab
Then 180° - ∠A - ∠B = ∠C (Angle sum of triangle)
You can just take a to be 2 units, b to be 3 units and c to be 4 units.
Alternatively,
Use variant ② of cosine rule :
② cos ∠C = (a² + b² - c²) / 2ab
then ∠C = cos-¹ [(a² + b² - c²) / 2ab]
sin ∠C = sin (cos-¹ [(a² + b² - c²) / 2ab])
See 1 Answer
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Hope this helps
Date Posted:
2 years ago
Thats not cosine rule
The format is correct.
He just wrote 'sin' by accident instead of 'cos'
He just wrote 'sin' by accident instead of 'cos'
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