Answer: 2. negative square root 21 over 5
Cos Θ = -2/5 = -0.4
Tan Θ > -1
Sin Θ = ?
Sin²Θ + Cos²Θ = 1
Sin²Θ = 1 – Cos²Θ
Sin²Θ = 1 – (–0.4)²
Sin²Θ = 1 – 0.16
Sin²Θ = 0.84
SinΘ = ± square root of 0.84
SinΘ = ±0.9165
If CosΘ is negative and TanΘ is positive, Θ lies in the third quadrant and therefore sinΘ is negative.
SinΘ = –0.9165 or negative square root of 21 over 5