Question

True or false:
cos(7x)-cos(5x)/sin(7x)-sin(5x)= tan(6x) is an identity

what???

Answer 1

Identity means "always true" and since the graph of these are literally mirrors of eachother it is not an identity.

Answer 2

\[\cos C-\cos D=-2\sin \frac{ C+D }{ 2 }\sin \frac{ C-D }{ 2 }\]
\[\sin C-\sin D=2 \cos \frac{ C+D }{ 2 }\sin \frac{ C-D }{ 2 }\]

Answer 3

i am not sure what you used to get there

Answer 4

\[\frac{ \cos C-\cos D }{ \sin C-\sin D }=-\tan \frac{ C+D }{ 2 }\]
C=7 x,D=5x

Answer 5

Which is 6, so its true. What formula is that?

Answer 6

negative sign

Answer 7

-tan 6x

Answer 8

ahhhh so its false i missread that. That is exactly what i expected thank you.

Answer 9

yw