Home » Ask & Discuss » Mathematics. » Trignometry « Back to Discussion

Trignometry

New kid on the Block

Joined:	11 Feb 2012
Post:	1

11 Feb 2012 21:20:17 IST

2 People liked this

382

Cos 1 Cos2 Cos3............Cos179

Mathematics

cos1.cos2.cos3...............cos179???? plss reply fast

Share this article on:

Comments (6)

sathyaram

Blazing goIITian

Joined: 25 Jul 2011

Posts: 322

11 Feb 2012 22:08:47 IST

Like 1 people liked this

We could use the formula:

cos(180-k)=-cos k

-cos 179 = cos (180-179)=cos 1.......

-cos 178 = cos (180-178)=cos 2 and so on....

We'll re-write the sum substituting the first terms, till cos 89, by their equivalents and we'll get:

-cos 179 -cos 178 -cos 177 - ... +cos 90 +...+cos 177 + cos 178 + cos 179.

Reducing the similar terms, we'll obtain:

S=0

Abhishek Bandiya

Cool goIITian

Joined: 7 Jul 2011

Posts: 59

11 Feb 2012 22:50:53 IST

Like 1 people liked this

we don t need anything just see

s=cos1 cos2 cos3.......................cos179

but look now

s=cos1 cos2 cos3.............cos90..........cos179

as cos90=0

so s=0

mr know all

New kid on the Block

Joined: 5 Feb 2012

Posts: 9

15 Feb 2012 10:47:32 IST

Like 0 people liked this

0because cos90=0 and it will come between the series

YASHARTH SRIVASTAVA

New kid on the Block

Joined: 18 Feb 2012

Posts: 4

22 Feb 2012 00:40:05 IST

Like 0 people liked this

it will be 0 bec cos 90 in between is o

YASHARTH SRIVASTAVA

New kid on the Block

Joined: 18 Feb 2012

Posts: 4

22 Feb 2012 00:41:47 IST

Like 0 people liked this

0 bec cos 90 is 0

ARJUN AJAY

New kid on the Block

Joined: 10 Feb 2012

Posts: 12

22 Feb 2012 17:22:40 IST

Like 0 people liked this

its 0......as cos90=0.

Quick Reply

Reply

	Some HTML allowed.
	Keep your comments above the belt or risk having them deleted.
	Signup for a avatar to have your pictures show up by your comment
	If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team

Free Sign Up!

Preparing for IIT-JEE ?

Arihant Revision Package for IIT JEE - Books, Practice Tests + Rank Predictor

@ INR 1,995/-

For Quick Info

Find Posts by Topics

Physics.

Topics

9401

20093

3672

2186

7617

2827

2638

Mathematics.

Chemistry.

Biology

Institutes

Parents

Board

Fun Zone