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

Trignometry

Forum Expert

Joined:	28 Feb 2007
Post:	2173

8 Feb 2008 09:52:35 IST

0 People liked this

455

Trig Eqn

None

Solve sin⁷x+cos⁷x = 1.

Share this article on:

Comments (6)

Sairam

Blazing goIITian

Joined: 14 Sep 2007

Posts: 573

8 Feb 2008 10:29:41 IST

Like 4 people liked this

i think 2 solns 0, pi/2

sin^7x<= sin^2x

cos^7x<=cos^2x

addin

sin⁷x+cos⁷x<= 1

but here gvn equality,

so sin^7x=sin^2x and cos^7x= cos^2x

so sinx=0/1..

x=0/pi/2

Hari Shankar

Forum Expert

Joined: 28 Feb 2007

Posts: 2173

8 Feb 2008 10:30:48 IST

Like 0 people liked this

Disposed!

Sairam

Blazing goIITian

Joined: 14 Sep 2007

Posts: 573

8 Feb 2008 10:32:45 IST

Like 0 people liked this

just to add on takin the eqns da other way round too yields da same result

i.e

sin^7x= cos^2x n cos^7x=sin^2x too yileds da same result

Sairam

Blazing goIITian

Joined: 14 Sep 2007

Posts: 573

8 Feb 2008 10:56:14 IST

Like 0 people liked this

edited

kk i mean i've gvn da solns in 0- 2pi..

u can get da gen sols easily

Hari Shankar

Forum Expert

Joined: 28 Feb 2007

Posts: 2173

8 Feb 2008 11:15:25 IST

Like 0 people liked this

No, its perfect. The conlclusion from the inequality is that either sinx = 0 and cosx =1 or sinx = 1 and cosx = 0. You can easi;y write the general solution set for these.

In my original post, I had titled the problem as Trig Eqn (or Ineqn!). Then edited it out bcos I thought it made the solution too obvious!

rockey

Scorching goIITian

Joined: 31 Oct 2007

Posts: 227

8 Feb 2008 12:45:50 IST

Like 2 people liked this

it is sin^7x=1 or cos^7x=1
therefore the solution is
x=2npi,2npi+pi/2

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