Question

Find the value of cos⁻¹ (cos7π/6).

Answer 1

Answer:

5π/6

Step-by-step explanation:

Given :

• cos⁻¹ (cos7π/6)

Solving :

• We know that : cos⁻¹ cosθ = θ
• But we can't just do that in this case
• Because the range of cos values is [0, π]
• Clearly, our value does not lie in this range
• We have to take a different Quadrant other than the 3rd Quadrant which gives cos a negative value
• The 2nd Quadrant also has cos values negative
• Therefore,
• cos⁻¹ cos (π - π/6)
• cos⁻¹ cos (5π/6)
• ⇒ 5π/6 ∈ [0, π] ⇒ It lies in the range!