Question

prove (cos4x+cos3x)/(sin4x-sin3x) = cotx/2 Can anyone help me explain the answer please

Answer 1

cos4x + cos3x = 2cos(7x/2)cos(x/2)
sin4x - sin3x = 2cos(7x/2)sin(x/2)
Their division is given.
On dividing cos(7x/2) Cancels out.
We are left with.
cos(x/2) / sin(x/2) = cot(x/2)

Answer 2

@siddhantsharan you typed fast!!!

Answer 3

HAha. Thanks. :D

Answer 4

how did you get 2cos(7x/2)cos(x/2)

Answer 5

someone help me pleaseeee

Answer 6

are the 4 and 3 meant to be exponents?

Answer 7

nooo

Answer 8

Then it's not an identity, you can't prove it.

Answer 9

but i got the first answer

Answer 10

I just wolfram alphad it, it's not an identity.

Answer 11

how do you do it then?

Answer 12

http://www.mathwords.com/s/sum_to_product_identities.htm
the 1st post has it correct, here is how they came up with it

Answer 13

you're saying wolfram alpha is wrongggggggggg?

Answer 14

i am, haha
post the link

Answer 15

OMG thank you! i dont have that pellet on my identity sheet

Answer 16

welcome, yeah i never learned these identities very well either