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What is one radian?
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All Flashcards in Topic 3.7
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3.7.18 cards
What is one radian?
The angle at the centre of a circle subtended by an arc equal in length to the radius (≈ 57.3°).
Convert degrees to radians.
Multiply by π/180 (since π rad = 180°).
Convert radians to degrees.
Multiply by 180/π.
How many radians in a full turn?
2π radians = 360° (and π radians = 180°).
Arc-length formula?
l = rθ, with θ in radians.
Sector-area formula?
A = ½r²θ, with θ in radians.
Express 60° in radians.
60 × π/180 = π/3 radians.
Why must θ be in radians for l = rθ and A = ½r²θ?
The formulas come from the fraction θ/(2π) of the circle; the 2π only cancels cleanly when θ is measured in radians.
Topic 3.7 study notes
Full notes & explanations for Radians (HL only)
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