CHAPTER 4. TRIGONOMETRY406. ()
− α βα+ β
α+β=
N í~å í~åí~å í~å
í~å ==- ()
+ α βα− β
α−β=
N í~å í~åí~å í~å
í~å ==- ()
α+ β
− α β
α+β=
í~å í~åN í~å í~å
Åçí ==- ()
α− β
+ α β
α−β=
í~å í~åN í~å í~å
Åçí ==
=
=4.10 Double Angle Formulas
=
- ëáåOα=Oëáåα⋅Åçëα=
=- ÅçëOα=ÅçëOα−ëáåOα=N−OëáåOα=OÅçëOα−N=
=- α− α
=
− αα
α=
Åçí í~åO
N í~åOí~å
í~åO O ==- O
Åçí í~å
OÅçíÅçí N
ÅçíOO α− α
=
αα−
α= == = = = = =