Conditional identityHardQuestion 200046
Question
If A + B + C = π (angles of a triangle), then tan A + tan B + tan C equals:
- Atan A tan B tan CCorrect
- Bsin A sin B sin C
- C0
- D1
Correct answer
tan A tan B tan C
Explanation
A+B+C = π → A+B = π−C. tan(A+B) = tan(π−C) = −tan C. (tanA+tanB)/(1−tanA tanB) = −tan C. Cross-multiplying: tan A + tan B + tan C = tan A tan B tan C.