Question

Question

0

680

1

if tanx = -1/3 and cosx>0
what is:
sin2x
cos2x
tan2x

Guest Mar 7, 2014

Dms · Answer 1 · 2014-03-07T10:47:43

Hello mathao21!

sinx=(-1/3)/(sqrt(1+(-1/3)^2))

cosx=1/(sqrt(1+(-1/3)^2))

And now, for sin 2x:

sin2x=2*((-1/sqrt(10))*(3/sqrt(10)))

...for cos 2x:

cos2x=1-2*(-1/sqrt(10))^2

...for tan 2x:

tan2x=(2*(-1/3))/(1-((-1/3)^2)))

To sum up:
If tanx=-1/3 and cosx>0 then:
[list]

sin2x= -3/5[/*:m]

cos2x= 4/5[/*:m]

tan2x= -3/4[/*:m][/list:u]

Have a nice day!
Dms