Why the answer is A, and why the others tempt you.
Using the Pythagorean identity, sin²θ + cos²θ = 1, so the expression becomes 1/cos θ = sec θ. Option B (tan θ) is a common distractor since tan θ = sin θ/cos θ, which is different from 1/cos θ.
Want this in Pidgin, Yoruba, Igbo or Hausa? Sign up free →
Practice more Mathematics questions
GCE Mathematics has thousands more questions like this — with Worked answers on every one.