Posted by Alex on Thursday, March 19, 2009 at 12:18pm.
Okay, I've been getting some of these, but I can't seem to verify this identity... any help? Here's the problem
Sin(x+y) + Sin(x-y) = 2sinxcosy
Okay, I've been working on the left side, and distribute, getting:
Sinx + Siny + Sinx - Siny
And, the sinx's add up to the 2sinx that I need for the right side, but the siny's cancel out if I don't change them around. So I changed one of them to 1/cscy... but I can't seem to work with that and the other siny to end up with cosy.
Where did I go wrong, or where do I go with it now?
- trig - Count Iblis, Thursday, March 19, 2009 at 12:25pm
Sin(x+y) = Sin(x)Cos(y) + Cos(x)Sin(y)
If you replace y by minus y and add you get twice the first term, because
cos(-y) = cos(y) and sin(-y) = - sin(y).
- trig - Alex, Thursday, March 19, 2009 at 2:28pm
oh, dang, forgot about that identity!
Okay, well, adding that up it ends up as 2sinx2cosy... but I need it to be 2sinx(1)cosy.
or am I really tired and I'm thinking too out of the box to realize the entire term of 2sinxcosy consists of 2sinx's and 2cosy's?
if not, what do I switch up to drop a cosy to satisfy the right side of the equation? oh man, am i sure forgetting everything about math, lol.
Answer This Question
More Related Questions
- trig - it says to verify the following identity, working only on one side: cotx+...
- TRIG! - Posted by hayden on Monday, February 23, 2009 at 4:05pm. sin^6 x + cos^6...
- Trigonometry - Prove the identity sin(x+y+z)+sin(x+y-z)+sin(x-y+z)+ sin(x-y-z...
- Algebra2 Verify Identity - Verify the Identity: csc(x)+sec(x)/sin(x)+cos(x)=cot(...
- Trig - verify the following identity: sin(x+y)*sin(x-y)=sin^2x-sin^2y
- Trigonometry - How do you solve this trig identity? Using @ as theta: Sin@-1/...
- trig...again - gahh i cant figure this one out either. you have you verify the ...
- Trig identities - Sin x/[1-cos(-x)] = csc x + cot x Please Verify the Identity. ...
- trig - verify the identity: sin(x+y)-sin(x-y)=2cosx siny
- Pre-Cal (verifying trig identities) - How would you verify the identity? sin^1/...