Question

If sin x = 3/5 and x is in quadrant 2, what is the value of tan x/2?

Answer 1

http://www.algebra.com/algebra/homework/Trigonometry-basics/Trigonometry-basics.faq.question.771795.html
this might help

Answer 2

Well I think it is supposed to be solved using trig identities

Answer 3

cosx = 1- 2 sin^2 (x/2)

cosx - 1 = -2sin^2(x/2)

-0.5cosx +0.5 = sin^2(x/2)

cosx = -4/5 (2nd quarter)

sinx/2 = sqrt(-0.5 * -4/5 + 0.5) = 3sqrt(10)/10



tanx/2 = -3sqrt(10)/sqrt(10) = -3 (2nd quarter)

Any mistakes ?

Answer 4

I get tan x = -3/4
since cos= -4/5
and sin=3/5
so (3/5)/(-4/5)=-3/4

Answer 5

but then since its tan x/2 I think you divide that by two
so tan x/2=(-3/4)/2
tanx/2=-3/8

Answer 6

NO

Answer 7

sin(60) = sqrt(3)/2
so sin(30) = sqrt(3)/ 4 ???

of course not , you have to use half angle identity

Answer 8

cosx = 1- 2 sin^2 (x/2)
cosx = 2cos^2(x/2) - 1
cosx = cos^2x/2 - sin^2x/2
sinx = 2 sinx/2 cosx/2

Answer 9

tanx = 2tanx/2 / 1- tan^2x/2

Answer 10

That's the double angle identities , you can derive the half angle ones from them.

Answer 11

Okay yeah I have those in my notes. But I dont understand where and how they are used when trying to solve these kind of questions.

Answer 12

??? liek I see that you plugged them in but how did you know that and when do you use this type of identity versus other ones?

Answer 13

It's easy to notice when to use them, if it's asking for ex for sin2x and the given is sinx so you have to use this identities , sin4x and you 're given sin2x or sinx or sin0.5x
it asks for sin0.5x and you have sin4x and so on.

Answer 14

always think of them when the angles are double or half in either sin or cos or tan or cot or cosec or sec xD

Answer 15

okay well it looks like tan x = 3 not -3

Answer 16

I am still very confused with this math. I am going to try another question and see if it will help my understanding

Answer 17

im pretty sure its x=3

Answer 18

@RCCB , x is in quadrant 2, is in the second quarter so it's negative.

Answer 19

180 >= x >= 90 (divide the whole equation over 2)
90 >= x/2 >= 45 (first quarter )

so x/2 in the 1st , x in the 2nd

Answer 20

oh