Sunday

February 1, 2015

February 1, 2015

Posted by **John** on Monday, February 10, 2014 at 8:08pm.

cot((x+y)/2)=-(sin(x)-sin(y))/(cos(x)-cos(y))

for all values of x and y for which both sides are defined.

- Precalculus -
**Steve**, Monday, February 10, 2014 at 8:34pmusing the half-angle formulas,

sin(x)-sin(y) = 2 cos((x+y)/2)sin((x-y)/2)

cos(x)-cos(y) = -2sin((x+y)/2)sin((x-y)/2)

ta-da!

- Precalculus -
**John**, Monday, February 10, 2014 at 9:03pmWow, I tried that but I messed up signs! Thanks!

- Precalculus -
**John**, Monday, February 10, 2014 at 9:09pmOops I meant sum and difference

- Precalculus -
**Steve**, Tuesday, February 11, 2014 at 12:27amNo,

**I**meant sum and difference. I started out trying the half-angle for tangent, but got bogged down. Then I saw the sums on the right and went the easy way.

**Answer this Question**

**Related Questions**

algebra - Can someone please help me do this problem? That would be great! ...

Trigonometry - Identities and proof - Show that cot((x+y)/2) = - (sin x - sin y...

Trigonometry - Please review and tell me if i did something wrong. Find the ...

TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...

tigonometry - expres the following as sums and differences of sines or cosines ...

Mathematics - Trigonometric Identities - Let y represent theta Prove: 1 + 1/tan^...

Math (Trig) - sorry, another I can't figure out Show that (1-cot^2x)/(tan^2x-1)=...

Trigonometry - Hello all, In our math class, we are practicing the trigonometric...

math - Prove that for all real values of a, b, t (theta): (a * cos t + b * sin t...

precalculus - For each of the following determine whether or not it is an ...