SVP,AIDEZ MOI A FAIRE CA. URGENT MERCI BEAUCOUP

Exercice 31
cos²(a)+sin²(a) = 1
(0,6)²+sin²(a) = 1
sin²(a)= 1-(0,6)²
sin²(a) = 1-0.36
sin²(a) = 0.64
d'ou sin(a) = V0.64 (V se lit racine de)
sin(a) = 0.8

Exercice 32
sin(a) = 4/5
cos²(a)+sin²(a) = 1
cos²(a)+(4/5)² = 1
cos²(a) = 1 - (16/25)
cos²(a) = (25 - 16)/25
cos²(a) = 9/25
d'ou
cos(a) = V(9/25)
cos(a) = 3/5

Exercice 33
cos(a) = (V5)/3
cos²(a)+sin²(a) = 1
((V5)/3)²+sin²(a) = 1
sin²(a)= 1-((V5)/3)²
sin²(a)= 1-(5/9)
sin²(a)= (9-5)/9
sin²(a)= 4/9
d'ou
sin(a) = (V4)/9 = 2/9

tan(a) = sin(a)/cos(a)
tan(a) = 2/9 / V(5)/3
tan(a) = 2/9 * 3/V5
tan(a) = 3*2 / 9V5
tan(a) = 2/3V5