Click to Chat

1800-2000-838

+91-120-4616500

CART 0

• 0

MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping
```        The value of cos 180/11+ cos 3*180/11+cos 5*180/11+cos 7*180/11+cos 9*180/11 is

0
-1/2
1/2
1

```
7 years ago

105 Points
```										Dear abhipsa,
we know that
cos a + cos 3a + cos 5a + .. + cos(2n-1)a = sin 2na/2 sin a
In our case n = 5
therefore RHS = sin 10a / (2sina)
=>RHS =  sin 2*5 *(180/11) / 2sin (180/11)
=> RHS = sin (180/11) /2 sin(180/11)
=> rhs = 1/2
hence the answer is option 3 ......1/2

GOODLUCK

Please        feel free to post as many doubts on our discussion forum as you    can.    We  are all IITians and here to help you in your IIT JEE    preparation.

```
7 years ago
anil dhar
8 Points
```										0
```
3 years ago
Think You Can Provide A Better Answer ?

## Other Related Questions on Trigonometry

View all Questions »
• Complete JEE Main/Advanced Course and Test Series
• OFFERED PRICE: Rs. 15,900
• View Details
Get extra Rs. 2,900 off
USE CODE: CHENNA
Get extra Rs. 636 off
USE CODE: CHENNA