Sagot :
bonjour
formule : cos (a - b) = cosa cosb + sina sinb (1)
cos x + sin x = √2 ( 1/√2 cos x + 1/√2 sinx ; [ 1/√2 = cos(π/4) = sin(π/4) ]
= √2 (cos(π/4)*cos x + sin(π/4)*sinx)
= √2 cos(π/4 - x) (formule (1) )
= √2 cos(x - π/4)
bonjour
formule : cos (a - b) = cosa cosb + sina sinb (1)
cos x + sin x = √2 ( 1/√2 cos x + 1/√2 sinx ; [ 1/√2 = cos(π/4) = sin(π/4) ]
= √2 (cos(π/4)*cos x + sin(π/4)*sinx)
= √2 cos(π/4 - x) (formule (1) )
= √2 cos(x - π/4)