what's the difference (not subtraction) between trig identities cos(x)sin(y) and sin(x)cos(y)? The distinction doesn't seem clear.

Question

welshfella · Answer

there is a difference in value the sine is a different ratio to the cosine

try working out sin30 * cos 40  and sin 40 * cos 30

welshfella · Answer

the only time they wont be different is when sin x = cos x
for example when x = 45 degrees

mpj4 · Answer

Is there a scenario where I have to arbitrarily set some angles to x and y? Because that's how this question came to mind.

welshfella · Answer

I can't bring one to mind..

fibonaccichick666 · Answer

check out product identities. http://www.purplemath.com/modules/idents.htm They are entirely different identities. Due to sine and cosine being different functions. Note that you could easily say let x=40 and y=30 or vice versa and pick which you are doing, but once you set the x and y, you have two distinct identities.

mpj4 · Answer

ah, that is helpful. Thanks.