Question

Adnan states if cos30°≈0.866, then sin30°≈0.866.

Which justification correctly explains whether or not Adnan is correct?

Answer 1

Adnan is incorrect because cosx and sin(90 - x) are always equivalent in any right triangle ⇒ first answer

Explanation:

In any right triangle there are two acute angles sum of them is 90°

∴ If one of them x°, then the other is (90 - x)°

∵ cos x = adjacent/hypotenuse

∵ sin(90 - x) = opposite/hypotenuse

∵ The opposite of ∠(90 - x) is the adjacent of ∠x

∴ cosx = sin(90 - x)