Question

Trig stuffs

Answer 1

If sinx = -3/5 and x is in quadrant 3, then tan2x = ?

I figured out that cosx is equal to -4/5.... and tanx should be 3/4... but 3/4 times 2 is 6/4 which is not one of the answer choices :/

Answer 2

Ahh, I think I got it! 24/7 right? And it would be positive?

Answer 3

tan(2x) = [2 tan(x)] / [1 - tan^2(x)]

and we got tan(x) = 3/4

tan(2x) = [2 (3/4)] / [1 - (3/4)^2]

tan(2x) = [3/2] / [1 - 9/16]

tan(2x) = [3/2] / [7/16]

tan(2x) = 3/2 * 16/7

tan(2x) = 3 * 8/7

tan(2x) = 24/7

Your answer is correct (:

Answer 4

It was marked wrong :( for some reason...

Answer 5

Oops, I forgot to think about positive and negative angles

tan x = 3/4

tan^-1 (3/4) = 36.87
It gives us the result in the 1st quadrant, but we know it is in the 3rd so add 180.

180 + 36.87 = 216.87

and that is x, find 2x

2x = 433.74

subtract by 360 to find the coterminal angle :p

it gets 73 which is in the first quadrant and it should be positive

not sure what we did wrong o.O

Answer 6

@agent0smith @triciaal @imqwerty

See where I went wrong? ._.

Answer 7

I checked over it and couldn't see it.