Page 107 - Math SL HB Sem 1

CIRCULAR FUNC'I'IONS AND TRIGONOMETRY

3.4 TRIGONOMETRIC IDENTITTES

Consider the point P(r,y) on the unit circle. *' * y2: I
: :
By substituting x cos d and y sin d into the equation of the unit circle.we get
+5irr2B:1 (l)
"os'a

Divide both sides of ( I ) by cos2 d . I + t,$20 =.""'d (2)

Divide both sides ol(l) by sin2d, r:ot2d + I =csc20 (-l )

DOUBLE ANGLE IDENTITIES

sin2A 2sinAcosA

cos2A:cos2A-sin2A
:
: 2 cos2A- 1
l - 2 sin2A

tan 2A = 2tan A
l-tan'A

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