NTA Abhyas JEE Main2020MathematicsTrigonometric Ratios & IdentitiesPractice
The arithmetic mean of the numbers 2 sin 2 o , 4 sin 4 o , 6 sin 6 o , … … . 178 sin 178 o , 180 sin 180 o is
Options
- Asin 1 o
- Bcot 1 o
- Ctan 1 o
- Dcos 1 o
Correct answer
B. cot 1 o
Step-by-step solution
Total number of given numbers = 90 Sum of numbers, S = 2 sin 2 o + 4 sin 4 o + . … … . . + 178 sin 178 o + 180 sin 180 o S = 178 sin 2 o + 176 sin 4 o + . … … . . + 2 sin 178 o Adding both the equation, we get, 2 S = 180 sin 2 o + sin 4 o + . … … . . + sin 178 o + 0 S = 90 sin 2 o + sin 4 o + . … … . . + sin 178 o ⇒ Mean = S 90 = sin 2 o + sin 4 o + . … … + sin 178 o = sin 89 o sin 1 o sin 2 o + 178 o 2 = cos 1 o sin 1 o × sin 90 o = cot 1 o