Answer:
324.13°
Explanation:
Applying,
cosA = 4/5
To find the value of A, we find the inverse of the cosine of both side,
(cosA)cos⁻¹ = cos⁻¹(4/5)
A = cos⁻¹(0.8)
A = 36.87° (First quadrant)
The above value of A is its value in the first quadrant
To find the value of A in the fourth quadrant, we use the expression
∅₄ = 360-∅₁............... Equation 1
Where ∅₄= value of A in the fourth quadrant, ∅₁ = value of A in the first quadrant.
Therefore,
∅₄ = 360-36.87
∅₄ = 324.13°
Hence the value of A in the fourth quadrant is 324.13°