#LC
a, `sin(x/2 - π/7) = (-√3)/2`
⇔ `sin(x/2 - π/7) = sin((-π)/3)`
⇔ \(\left[ \begin{array}{l}\frac{x}{2}-\frac{π}{7}=\frac{-π}{3}+k2π\\\frac{x}{2}-\frac{π}{7}=π+\frac{π}{3}+k2π\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=\frac{-8π}{21}+k4π\\x=\frac{62π}{21}+k4π\end{array} \right.\)
b, `sin(2x + 10°) = -1`
⇔ `sin(2x+10°) = sin(270°)`
⇔ `2x+10° = 270° + k.360°`
⇔ `x = 130° + k.180°`
c, `sin5x = 3`
Có: `-1≤sin5x≤1` `∀ x ∈ R`
⇒ `x ∈ ∅`
d, `sinx = -1`
⇔ `sinx = sin((3π)/2)`
⇔ `x = (3π)/2 + k2π`
