70 
MEMOR1AS CIENTIF1CAS I LITERARIAS 
. • . X 
z 2 ~ 1 t _ 4 zdz 
z 2 + 1 ’ X ~ (z 2 + 1) 2 
2 
—2 arc tg ~|/ J_iiL 
= arc sen x. 
o. 
J- 
V a-j-b x-f-x 2 
Sean a, (3 las raices reales : 
Va + bx-j-x 2 = y(x-a) (x — /8)=(x — a) z 
/3 — x = (x — a) z 2 
/3+a z :3 
1+z 2 
, 2 (a — j3) 7 a r dz 
d x = d z, y = — 2 J 
(i+z 2 r 
l+z 2 
= — 2 arc tg 
l/|=i 
dx 
x 
yr 
Sea Vi— x 2 =xz — 1, 
1— x 2 =x 2 z 2 — 2xz4-l o x = 
2 z 
l+z‘ : 
z 2 — 1 , 2 + 2 z 2 — 4z 2 
dx = - 
z 2 +l 
1 + z 2 
x 
1 + ]/l— X 2 
