Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
pottersheep
Group Title
I really need help with this Trig identity please!(Grade 12!)
How do I prove that sinxsiny = 2cos([x+y]/2)sin([x+y]/2)
 2 years ago
 2 years ago
pottersheep Group Title
I really need help with this Trig identity please!(Grade 12!) How do I prove that sinxsiny = 2cos([x+y]/2)sin([x+y]/2)
 2 years ago
 2 years ago

This Question is Closed

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
I've been at it for so long! I cant get it :(
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
I can help.
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
Thank you so much
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
We have only learnt compound angles, by the way
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
So there is an identity that's called co function identies, do you know them?
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
I think so
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
Or sum to product identities. Do any of these sound familiar.
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
Is it the cos(90x) kind of thing?
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
um, not really. Here, let me post a link.
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
http://www.sosmath.com/trig/Trig5/trig5/trig5.html
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
Thanks Ill read it!
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
nope....never learnt those :s
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
Give me like 510 minutes. This one is a little tricky. I'll try to keep you updated with the steps.
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
Alright I really appreciate it
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
I found a note that our teacher wrote on the board! I dont get it though... he wrote
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
sinx + siny = sin(a+b) = sinacosB + cosAsinB sin(ab) = sinAcosB  cosAsinB sin(a+B) + sin (a  b) = 2sinAcosB
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
ignore the caps they are the same letter
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
Then he wrote : let : a+b = x a  b = y 2a = x+y x = (x+y)/2
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
still working....
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
Okay, Do you know the double angle formula?
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
okay, so cos([x+y]/2)sin([x+y]/2). This equal sin(x+y)
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
Are you following what i mean here?
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
how about this. 2cosAsinA=sin2a. A=(x+y)/2
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
alright
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
cosine of x is sine of (90x) right?
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
okay. so =sin(x+y) =sinxcosy+sinycosx =sinx sin(90y)+siny sin(90x)
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
I have a quick question, is it sin(x+y)/2 or sin(xy)/2?
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
one sec for the original question?
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
oh no! you are right it sin(xy)!!!!!!!
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
sorry ><
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
Ok, that makes more sense now.
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
Give me another minute to type this up.
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
Of course
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
ok, i've got it.
 2 years ago

zordoloom Group TitleBest ResponseYou've already chosen the best response.1
ok let me know if you can see it.
 2 years ago

pottersheep Group TitleBest ResponseYou've already chosen the best response.0
I can see it! Im following through fine so far. Thank you so much
 2 years ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.