PRELIMINARY 
oh ras pee gm Bosal - sin? B = cos* B — cos® A. 
cos (A + B) cos (A — B) = cos* A — sin? B = cos? B — sin? A. 
sing = + YE(T= ond) cos A). A_ sinA 
peed: J/1+sin AL 
sin 3-008 = + ,/1—-sinA. 
yoy heceg ame ee abe A-B). 
2 cos A sin B=sin (A + B) —sin(A-B 
2 cos A cos B= cos (A + B) + cos (A ~B 
— 2 sin A sin B =cos (A + B) — cos (A — B). 
sin A +sin B=2 sin “+P eos A-®. 
Gia A atin Baten 442 ag AWB 
cos A +cos B= 2008 A+B eos A-F. 
A+R AR -B 
cos A —cos B= — 2 sin 5 sin 
4. Formule for Triangles.—a, }, and ¢ are the sides of a triangle, 
and A, B, and C are the opposite angles. 
athb+e= 2s, A+B+C=180". 
a b c 
> Jon Se = bcos C+ ene Bi 
aA ain B an© eens ae 
a? = b? +2 — Qhe cos A. ge see 
2he 
sin 4. ape aR 
A 8(s — a) A_ (s- b)(s—¢) | 
“op a be ~ 2 ~s(s—a) 
sin A= o Valea) 0). 
tan Bt cot 
2 a+b 
| Area of triangle =A — Pe sin A= ,/s(s— a) (s— 0) (s—c). 
, 
