Solving sin(alpha+beta)=sin(alpha)+sin(beta)

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Nicely symmetric solution. What's about cos (alfa + beta) = cos alfa + cos beta ?
P.S. I am trying to solve this variant, but it seems to be too hard :)

panPetrff
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From the the given expression : sin(A-B) = sinA - sinB then add the 2 expressions and apply the law of addition of 2 sines :
sin(A+B) + sin(A-B) = 2sinA = 2sinAcosB implies sinA(cosB -1) = 0 etc...
Remark : given expression is symmetric with respect to A and B, and trivial solutions : A=B=0, A=0 ...

WahranRai
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As we can see sin(a + b) = sinacosb + sinbcosa so that cosa = 1 and cosb = 1 and we can finally find the answer is a = b = k2pi. Anyway, your answer is really nice ! Keep it up !

vanphi
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sin(a+b)=sinacosb +sinbcosa. This is always less than equal to sina+sinb. That's bcoz cosa, cosb=<1. Thus in our case, cosa=cosb=1. So, we can find the general expressions for a and b.

titassamanta
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nice solution. i always look forward to see your video. always coming with good ideas.

kpt
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Solving before the video from the thumbnail -

sin(α+β) = sinβcosα + cosβsinα
Let cosα=1 and then sinα must be 0 making the following statement true -
sin(α+β) = sinβ + sinα
α=n2π where n ∈ *Z*
Because sinβ equals itself.
Alternatively, β=n2π where n ∈ *Z* by the same reasoning.

Time to see what I missed, it's always something. 👍😀

Edit - oh - sinθ=-sin(-θ) symmetry on either side of the cos axis. Obviously. Well - I always miss something. Thanks for the problem!

Ni
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the sum of sins can turn into 2 times sin of half the sum of angles times cos half the difference of angles. and the sin of sum of angles can turn into 2 times sin of half the sum of angles times cos half the sum of angles. then take out the common factor of 2 times sin and equate to zero and solve. and then equate the cos of half the sum of angles to cos of half the difference of angles and solve

magick
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Kanalın daha fazla büyümesi dileğiyle <3

dollynoob
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Sin(a+b) = sinacosb + sinbcosa so cosa = cosb = 1.
So a = kpie
And b = kpie

damiennortier
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Why not written the (2π-β, β)?
(Only (α, 0) & (0, β) case is so)

jarikosonen
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I just went the other way around, by squaring both sides and simplifying all the way down 😅

franciscoj.f.
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I dont understad where the expresion come from.

arturovinassalazar
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I solved this replacing sin and cos using the euler's formula

ΒασιληςΚεκεσης
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At the end of the video you made a confusing explanation for the solution alpha, 2pi-alpha.

valentinodrachuk
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alpha = 0, n*pi, beta = 0, n*pi n both odd and even

sanjuiyengar
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Comments from. F...If square on both sides the nature of the equation changes... without squaring on both sides it's to be solved.

visweswararoach
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1:42

I'm struggling to figure out what Mike Pence has to do with trigonometry.

diedoktor
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I have a simpler answer: if I sin with my GF then I sin and she also sins and we both sin together. Problem solved 😈

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