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secondary 3 | E Maths
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Help pleaseee
Date Posted: 4 years ago
Views: 331
Hi Tarah!
First part is 72 degrees since the centre is dissected into five equal parts.
Will do the rest by 3 am if no one has done them yet.
First part is 72 degrees since the centre is dissected into five equal parts.
Will do the rest by 3 am if no one has done them yet.
Draw the line OA, OB , OC ,OD. now you'll see that the circled is divided into 5 equal parts. The triangles inside are all congruent since this is a regular Pentagon.
The angle in the centre is 360° and its made of 5 equal angles (each triangle's corresponding angles are equal)
So one angle is just 360° ÷ 5 = 72°
b)
Since the circle is now cut into 5 equal parts, the arc AB, BC,CD,DE and EA are all
So the arc AB is just 1/5 of the circumference of the circle.
Arc AB = 1/5 x 2πr
= 1/5 x 2π x 14cm
≈ 17.5929189cm
= 17.6 cm (3.s.f)
c)
Shaded area = circle area - pentagon area
= Circle area - area of 5 congruent triangles
= πr² - 5(½ab sin c)
= π(14²) - 5(½(14)(14)sin72°)
≈ 149.734467 cm²
= 150 cm² (3s.f)
The angle in the centre is 360° and its made of 5 equal angles (each triangle's corresponding angles are equal)
So one angle is just 360° ÷ 5 = 72°
b)
Since the circle is now cut into 5 equal parts, the arc AB, BC,CD,DE and EA are all
So the arc AB is just 1/5 of the circumference of the circle.
Arc AB = 1/5 x 2πr
= 1/5 x 2π x 14cm
≈ 17.5929189cm
= 17.6 cm (3.s.f)
c)
Shaded area = circle area - pentagon area
= Circle area - area of 5 congruent triangles
= πr² - 5(½ab sin c)
= π(14²) - 5(½(14)(14)sin72°)
≈ 149.734467 cm²
= 150 cm² (3s.f)
See 1 Answer
done
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Hope this helps! Feel free to clarify.
Date Posted:
4 years ago
Tarah, do take note of the following as stated in the syllabus 4048 for E math :
'Unless stated otherwise within a question, three-figure accuracy will be required for answers. This means that four-figure accuracy should be shown throughout the working, including cases where
answers are used in subsequent parts of the question. Premature approximation will be penalised, where appropriate. Angles in degrees should be given to one decimal place. '
So in your working, avoid rounding off to 3 s.f until the final answer for each section of the question.
'Unless stated otherwise within a question, three-figure accuracy will be required for answers. This means that four-figure accuracy should be shown throughout the working, including cases where
answers are used in subsequent parts of the question. Premature approximation will be penalised, where appropriate. Angles in degrees should be given to one decimal place. '
So in your working, avoid rounding off to 3 s.f until the final answer for each section of the question.
Thank you J for pointing that out!
Sorry Tarah for the imperfect answer but do take note of the aforementioned detail.
Wishing you atb!
Sorry Tarah for the imperfect answer but do take note of the aforementioned detail.
Wishing you atb!
most welcome, Marcus
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