BJR , combien fait cos(12) mrc d'evnce

bjr

π/12 = π/3 - π/4

on utilise

cos (a - b) = cosa cosb + sina sinb

cos(π/12) = cos[(π/3) - (π/4)]

              = cox(π/3) cos(π/4) + sin(π/3) sin(π/4)

= 1/2 x √2/2 + √3/2 x √2/2

= √2/4 + √6/4

            = (√2 + √6)/4

valeur exacte