dp z-r(cor.??+s(In.?f) 
^ cp = z-r(^cor.4f +efin.lf) 
cUn ep =: z_r(cor.^^l=^+sfin.^;il^) 
03 rtf §. 15 fluttes, at Q€qationcii6 x" — r" = o 9{at)i<e« «« 
altfa.i 6fber i gøfgc 17 z" — 1" = ap.bp,cp,dp»cp. Sø(()e(if} n 2m(^^m 
af z'^ — r" faa (kr fom 9)coDuctct af Einiecuco ap, bp^ cp :c. e«n3^cr, §. 4* 
Om pfane gjofpsoncré Opfoéniiig^ 
gøljjenbe af 'Jrigonometnen ^eficnbt^ anfører jeg uim 5Semi^» 
fl) fin. (a + b) = fin. a ♦ cof. b + fin. b ♦ cof. 
3) cof. (a+b) = cof. a ♦ cof. b — fin. a » fin. b* 
f) fin. 2a == 2 fin. a ♦ cof. 
cf) I cof. 2a = 2 cof.^ a* 
^) I — cof. 2a = 2 fin/ a» 
/] tang:, a = — ^ 
g) fin. a fin. b = 2 fin. ^i-^ ^ cof. ^ '^^ ^ 
h) fin. a — fin. b = 2 cof. ♦ fin. ^ — 
^_ 22 
s) cof. b — cof. a = 2 fin. ^ fin. — 
2 3 
fm. a 4- fin. b a-j-b 
^) cT l.a4.col.b = "Dg.^. 
fin, a ~- fin, b a— -b 
^' ^Z7+Æ = tang, — -, 
§. 20. 
