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denniel
 3 years ago
Prove this identity sin(2A)=2sinAcosA.
denniel
 3 years ago
Prove this identity sin(2A)=2sinAcosA.

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Tonks
 3 years ago
Best ResponseYou've already chosen the best response.1Start by considering 2A as A+A ... does that make you think of any particular theorem?

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.0...of course that makes me want to know how to prove the theorem you are thinking of @Tonks

muhammad9t5
 3 years ago
Best ResponseYou've already chosen the best response.0sin(a+a)=sinacosb+cosasinb put the value of a and be here.

micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.0We know that sin(2A) = sin(A + A) sin (A + A) = cosA sinA + cosA sinA = 2 sinA cosA QED

Tonks
 3 years ago
Best ResponseYou've already chosen the best response.1@TuringTest try stacking triangles in the unit circle... or is that for cosine?

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.0I know it was some geometric proof like that, I don't remember those darn things...

micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.0Is that enough or do you need proof for sin (A + B) = cosA sinB + cosB sinA

muhammad9t5
 3 years ago
Best ResponseYou've already chosen the best response.0formula you have given is wrong @micahwood50

micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.0For proof of sin (A + B) = cosA sinB + cosB sinA: http://en.wikipedia.org/wiki/Proofs_of_trigonometric_identities#Sine

muhammad9t5
 3 years ago
Best ResponseYou've already chosen the best response.0http://upload.wikimedia.org/math/3/e/c/3ec0e99aa364deb052280bcd801fcec2.png

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.0yep, that's the one...

micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.0@muhammad9t5 It's the same. Your point is?

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.0perhaps you are neglecting the fact that multiplication is commutative muhammad?

micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.0dw:1350147756505:dw

muhammad9t5
 3 years ago
Best ResponseYou've already chosen the best response.0ok i got it!! he has just rearranged the places of cos and sin.

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.0in English that's called the commutative property of addition.

micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.0Yeah, sorry about that, though. It's easier for me to remember this formula this way.

muhammad9t5
 3 years ago
Best ResponseYou've already chosen the best response.0@micahwood50 can this destroy the problem of sin(4530) solve with your formula.

muhammad9t5
 3 years ago
Best ResponseYou've already chosen the best response.0cos45*sin30cos45sin30

micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.0Well, with minus, it's different story.

muhammad9t5
 3 years ago
Best ResponseYou've already chosen the best response.0ok do sin(45+30)=cos45sin30+cos30sin45

micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.0Yeah, I got it. Thanks, though.

muhammad9t5
 3 years ago
Best ResponseYou've already chosen the best response.0bro never mind if i disturb you! Accept just like the game of trig!

micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.0@muhammad9t5 I know the formulas, you don't have to correct me. Thanks, though.
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