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secondary 3 | A Maths
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Trin
Trin

secondary 3 chevron_right A Maths chevron_right Singapore

Trigonometry identities

Date Posted: 2 years ago
Views: 238
J
J
2 years ago
1 - a tan θ = sec θ

1 - a sin θ / cos θ = 1 / cos θ

Multiply throughout by cos θ,

cos θ - a sin θ = 1

a sin θ = 1 - cos θ

a = (1 - cos θ) / sin θ



b - cot θ = cosec θ

b - cos θ / sin θ = 1 / sin θ

b = 1 / sin θ + cos θ / sin θ

b = (1 + cos θ) / sin θ


Then,

ab = (1 - cos θ) / sin θ × (1 + cos θ) / sin θ

ab = (1 - cos θ)(1 + cos θ) / sin² θ

ab = (1² - cos²θ) / sin² θ

ab = sin² θ / sin² θ

ab = 1

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