First slide

Trigonometric equations

Question

$T h e n u m b e r o f s o l u t i o n s o f \sum_{r = 1}^{5} \cos r x = 5 i n t h e i n t e r v a l [0, 2 π] i s$

Easy

A

0
B

1
C

5
D

2

Solution

$\sum_{r = 1}^{5} \cos r x = 5 \Rightarrow \cos x + \cos 2 x + \cos 3 x + \cos 4 x + \cos 5 x = 5$
$w h i c h i s p o s s i b l e o n l y w h e n \cos x = \cos 2 x = \cos 3 x = \cos 4 x = \cos 5 x = 1 a n d i s s a t i s f i e d b y x = 0 a n d x = 2 π$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App