Question

Which expression is equivalent to tan(-x)cos2x?


A.

-sin xcos x




B.
sin xcos x




C.
tan x + sin2x




D.
tan x − sin2x




E.
-tan x − sin2x

Answer 1

@souvik i dont understand

Answer 2

do you know this ...tan(-x)=-tanx?

Answer 3

yea

Answer 4

and this cos2x=cos^2x-sin^2x...........?

Answer 5

yes

Answer 6

then use these formulas...

Answer 7

i dont know how to exactly

Answer 8

tan(-x)*cos2x
=-tanx[cos^2x-sin^2x]

Answer 9

i got that but then what?

Answer 10

then tanx=sinx/cosx

sinx/cosx[cos^2x-sin^2x]

Answer 11

what now do they cancel out or something?

Answer 12

\[-\frac{ sinx }{ cosx }*\cos^2x +\frac{ sinx }{ cosx }*\sin^2x\]

Answer 13

-sinxcosx+tan(x)? thats not one of the choices

Answer 14

@souvik?

Answer 15

you there??

Answer 16

yeah i am here..

Answer 17

-sinxcosx+tan(x) is what i got

Answer 18

we should do it in this way...
using this...cos2x=2cos^2x-1

Answer 19

-tanx[2cos^2x-1]
=-sinx/cosx[2cos^2x-1]
=-2sinx*cosx+sinx/cosx
=-sin2x+tanx
=tanx-sin2x

get it?

Answer 20

kinda, buti think i will get better with more practice problems. thank you for your help.

Answer 21

the more u practice the more u learn......:)