Thursday

December 18, 2014

December 18, 2014

Posted by **Kinjal** on Tuesday, February 12, 2013 at 10:18am.

- Maths -
**Steve**, Tuesday, February 12, 2013 at 10:54ambecause the difference of an AP is constant,

sec(x) - sec(x+y) = sec(x-y) - sec(x)

or, converting to cosines for ease of calculation,

cos(x+y) cos(x-y) - cos(x) cos(x-y) = cos(x) cos(x+y) - cos(x+y) cos(x-y)

2(cosx cosy - sinx siny)(cosx cosy + sinx siny) = cosx(cosx cosy + sinx siny) + cosx(cosx cosy - sinx siny)

cos^2(x)cos^2(y) - sin^2(x)sin^2(y) = cos^2(x)cosy

cos^2(x)cos^2(y) - (1-cos^2(x)-cos^2(y)+cos^2(x)cos^2(y)) = cos^2(x)cos(y)

cos^2(x)(cos(y)-1) = cos^2(y)-1

cos^2(x) = cos(y)+1

cos^2(x) = 2cos^2(y/2)

cos(x) = ±√2 cos(y/2)

**Answer this Question**

**Related Questions**

Confused! Pre-Cal - Verify that each equation is an identity.. tan A= sec a/csca...

Calculus - Q: If y=sinx/(1+tanx), find value of x not greater than pi, ...

Integration - Intergrate ¡ì sec^3(x) dx could anybody please check this answer. ...

Math - 1. Find y'(x) when xsecy - 3y sinx = 1 a) (3ycosx - sec y) / (xsec^2y - ...

Trigonometry - Prove the following trigonometric identities. please give a ...

TRIGONOMETRY *(MATHS) - Q.1 Prove the following identities:- (i) tan^3x/1+tan^2x...

Pre-Calc - Trigonometric Identities Prove: (tanx + secx -1)/(tanx - secx + 1)= ...

math - How would you establish this identity: (1+sec(beta))/(sec(beta))=(sin^2(...

Trigonometry - How do you verify the equation is an identity? Tan^2x-tan^2y=sec^...

math - Determine all the possible values of x where 0 deg is more than or equal ...