(ii) Find the average of sin2∘,sin4∘,sin6∘,……,sin180∘ (iii) Prove that cos11π+cos113π+cos115π+cos117π+cos119π=21 Answers : 90cot10 [2] Find sum of the following series: (14) cos2n+1π+cos2n+13π+cos2n+15π+…… up to n terms. (15) sin2α+sin3α+sin4α+…..+sinnα, where (n+2)α=2π

Name: Video solution 1: (ii) Find the average of sin2∘,sin4∘,sin6∘,……,sin180∘ (iii) Prove that cos11π+cos113π+cos115π+cos117π+cos119π=21 Answers : 90cot10 [2] Find sum of the following series: (14) cos2n+1π+cos2n+13π+cos2n+15π+…… up to n terms. (15) sin2α+sin3α+sin4α+…..+sinnα, where (n+2)α=2π
Uploaded: 2022-09-14T12:06:38.000Z
Duration: 11 min
Description: Video solution 1: (ii) Find the average of sin2∘,sin4∘,sin6∘,……,sin180∘ (iii) Prove that cos11π+cos113π+cos115π+cos117π+cos119π=21 Answers : 90cot10 [2] Find sum of the following series: (14) cos2n+1π+cos2n+13π+cos2n+15π+…… up to n terms. (15) sin2α+sin3α+sin4α+…..+sinnα, where (n+2)α=2π

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(ii) Find the average of 2^{}, 4^{}, 6^{}, , 180^{} (iii)

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(ii) Find the average of sin2∘,sin4∘,sin6∘,……,sin180∘
(iii) Prove that

(ii) Find the average of $sin 2^{\circ}, sin 4^{\circ}, sin 6^{\circ}, \dots\dots, sin 18 0^{\circ}$ (iii) Prove that $cos \frac{π}{11} + cos \frac{3 π}{11} + cos \frac{5 π}{11} + cos \frac{7 π}{11} + cos \frac{9 π}{11} = \frac{1}{2}$ Answers : $\frac{c o t 1 ^{0}}{90}$ [2] Find sum of the following series: (14) $cos \frac{π}{2 n + 1} + cos \frac{3 π}{2 n + 1} + cos \frac{5 π}{2 n + 1} + \dots\dots$ up to $n$ terms. (15) $sin 2 α + sin 3 α + sin 4 α + \dots .. + sin n α$ , where $(n + 2) α = 2 π$

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(ii) Find the average of

sin 2^{\circ}, sin 4^{\circ}, sin 6^{\circ}, \dots\dots, sin 18 0^{\circ}

(iii) Prove that

cos \frac{π}{11} + cos \frac{3 π}{11} + cos \frac{5 π}{11} + cos \frac{7 π}{11} + cos \frac{9 π}{11} = \frac{1}{2}

Answers :

\frac{c o t 1 ^{0}}{90}

[2] Find sum of the following series: (14)

cos \frac{π}{2 n + 1} + cos \frac{3 π}{2 n + 1} + cos \frac{5 π}{2 n + 1} + \dots\dots

up to

n

terms. (15)

sin 2 α + sin 3 α + sin 4 α + \dots .. + sin n α

, where

(n + 2) α = 2 π

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Question Text	(ii) Find the average of $sin 2^{\circ}, sin 4^{\circ}, sin 6^{\circ}, \dots\dots, sin 18 0^{\circ}$ (iii) Prove that $cos \frac{π}{11} + cos \frac{3 π}{11} + cos \frac{5 π}{11} + cos \frac{7 π}{11} + cos \frac{9 π}{11} = \frac{1}{2}$ Answers : $\frac{c o t 1 ^{0}}{90}$ [2] Find sum of the following series: (14) $cos \frac{π}{2 n + 1} + cos \frac{3 π}{2 n + 1} + cos \frac{5 π}{2 n + 1} + \dots\dots$ up to $n$ terms. (15) $sin 2 α + sin 3 α + sin 4 α + \dots .. + sin n α$ , where $(n + 2) α = 2 π$
Updated On	Sep 14, 2022
Topic	Trigonometry
Subject	Mathematics
Class	Class 11
Answer Type	Video solution: 1
Upvotes	110
Avg. Video Duration	11 min

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