bonjour
ex 55
on connaît quelques valeurs remarquables (voir image)
a) α = 30°
sin α = 1/2
b) α = -π/2
sin (-π/2) = - sin (π/2) = -1 [sin (-a) = -sin a ]
c) α = 13π/6
sin(13π/6) = sin (12π/6 + π/6)
= sin (2π + π /6) [ sin (a + 2π) ] = sin a ]
= sin (π/6) = 1/2
