In trigonometry, which identity is mathematically equivalent to for all real numbers ?
Answer and explanation
Correct answer: B.
- Step 1: Double-angle identity: . Step 2. Substitute : . **Answer: . Why not the others:** is ; is .
Practise more Mathematics A: Functions, Calculus, Complex Numbers and Probability.
Free questions with an explanation for every one, and full timed Exames Nacionais Secundário (Portugal) mock tests.