Defintion
- Sin(A) = y/r or sin(A) = Opp/Hyp Why do we name y/r as sine ?
- Originally sine function is called chord function.
- Draw a circle.
- Draw a P on circle and we can draw two chord PA and PB.
- Let PA be perpendicular to PB then AB is diameter.
- Let Angle PAB = A and sin(A) = PA/AB = 2*y/(2*r) = Opp/Hyp.
- Hence cos(A) = 2*x/(2*r) = Adj/Hyp.
- Hence sin(A) and cos(A) are two chords.
- Tan(A) = y/x or tan(A) = Opp/Adj. Why do we name y/x as tangent ?
- Draw a circle.
- Draw a tangent to circle at OX
- Pick a point P on tangent and draw a line to center O.
- Angle POX = A and tan(A) = PX/OX = y/x = Opp/Adj.
- Hence Tangent PX = OX*tan(A).
- Tan(A) = y/x or tan(A) = Opp/Adj. Why do we name y/x as tangent ?
- Draw a circle.
- Draw a secant to circle at point P vertically.
- Draw a secant to circle at point P horizontally.
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