Page 107 - Math SL HB Sem 1

CIRCULAR I.'TJNC-I'IONS AND TRIGONoMIiT-RY

3-4 TRIGONOMETRIC IDENTITIES

Consider the point P(x,y) on the unit circle, x2 + y2 = 1
:
By substiruting x: cos d and y sin d into the equation of &e unit circre.we get

+ sinzd I (t)
"or'B --

Divide both sides of ( I ) by cosr d . | +a3,n20 =se"ld (2)

Divide both sides ol(l) by sin2d, cot2o + I =csc2d (l)

DOT]BLE ANGI,E IDI,]NTITIES

sin2A = 2sinAcosA

cos2A="oszA-sirr2A
:
: 2 cos2A- 1
l - 2 sin2A

ztan A
lan2A : ------------^
l-tan'A

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