If sin⁡(θ)=4/5 and θ is NOT in the first quadrant, then find the value of cos θ.

Correct option is A

Given:
sin θ = 4/5, and θ is NOT in the first quadrant.
Solution:
Using the identity: sin$$^2$$​ θ + cos$$^2$$​ θ = 1.
Substitute sin θ = 4/5: (4/5)$$^2$$​ + cos$$^2$$​ θ = 1
16/25 + cos$$^2$$​ θ = 1
cos$$^2$$​θ = 1 - 16/25 = 9/25
cos θ = ±3/5
Since θ is not in the first quadrant, cos θ is negative. Therefore, cos θ = -3/5.
Thus, the value of cos θ is -3/5.