Question:
Which of the following is not correct?
A. sin θ = – 1/5
B. cos θ = 1
C. sec θ = ½
D. tan θ = 20
Solution:
C. sec θ = ½
Explanation:
According to the question,
We know that,
a) sin θ = – 1/5 is correct since Sin θ ∈ [-1,1]
b) cos θ = 1 is correct since Cos θ ∈ [-1,1]
c) sec θ = ½
⇒ (1/cos θ) = ½
⇒cos θ=2 is incorrect since Cos θ ∈ [-1,1]
d) tan θ = 20 is correct since tan θ ∈ R.
Thus, option (C) sec θ = ½ is the correct answer.