Question

aflati sin =1/3 , xE (PI/2, PI)

a) sin2x=
b)cos 2x=
c)tg2x=

Answer 1

Răspuns:

Explicație pas cu pas:

a)sin2x=2sinxcosx

cosx=√1-sin²x=√(1-1/9)=-2√2/3   x∈(π/2,π)  cosinus e negativ

sin 2x=1/3(-2√2/3)=-2√2/9

b)cos2x=1-2sin²x=1-2×8/9=(9-16)/9=-7/9

c)tg2x=sin2x/cos2x=-2√2/9:(-7/9)=2√2/7