Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
Trig Identities Question: say we have sin(x+deltax) = sinx*cosdeltax + cosx*sindeltax
and we want to introduce sinx on both sides.
So, how can I put sinx on the left, and a 1 on the right like this:
sin(x+deltax)  sinx = sinx*(cosdeltax1) + cosx*sindeltax
Professor Strang is doing this in a video lecture, and I want to understand what the basis for this is. Can you help me understand this?
 2 years ago
 2 years ago
Trig Identities Question: say we have sin(x+deltax) = sinx*cosdeltax + cosx*sindeltax and we want to introduce sinx on both sides. So, how can I put sinx on the left, and a 1 on the right like this: sin(x+deltax)  sinx = sinx*(cosdeltax1) + cosx*sindeltax Professor Strang is doing this in a video lecture, and I want to understand what the basis for this is. Can you help me understand this?
 2 years ago
 2 years ago

This Question is Closed

jim_thompson5910Best ResponseYou've already chosen the best response.0
I'm going to use y instead of deltax to save time. sin(x+y) = sin(x)*cos(y) + cos(x)*sin(y) Now subtract sin(x) from both sides sin(x+y)  sin(x) = sin(x)*cos(y) + cos(x)*sin(y)  sin(x) Group like terms and factor sin(x+y)  sin(x) = (sin(x)*cos(y)  sin(x)) + cos(x)*sin(y) sin(x+y)  sin(x) = sin(x)*(cos(y)  1) + cos(x)*sin(y) Now if you want, you can replace y with deltax again to get sin(x+deltax)  sin(x) = sin(x)*(cos(deltax)  1) + cos(x)*sin(deltax)
 2 years ago

satellite73Best ResponseYou've already chosen the best response.1
you are thinking way too hard. it is not trig, it is algebra
 2 years ago

satellite73Best ResponseYou've already chosen the best response.1
what jimthompson wrote. it is not a trig identity at all
 2 years ago

FreeTraderBest ResponseYou've already chosen the best response.0
Thanks, I seem to have lost my mind due to cos and sin being on the scene.
 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.