Another trig. question

1. The problem statement, all variables and given/known data
Given that 5sec^2+3tan^2 = 9
find sinx value

2. Relevant equations
trig. identities


3. The attempt at a solution
i started off by subbing. in sec2= 1+tan^2
=>
5(1+tan^2)+3tan^2= 9
5+8tan^2x = 9
8tan^2 = 4
tan^2 = 1/2 <--- no idea of this bit, as i am supposed to find sin x value =/ , hmm i even wonder if this right.
 

rock.freak667

Homework Helper
6,232
27
Yes it is correct. Take the square root and find the angles for the two values.
 
tanx= [tex]\sqrt{}1/2[/tex]
x= inverse. sin [tex]\sqrt{}1/2[/tex] is that how i get values for sin?
 

rock.freak667

Homework Helper
6,232
27
tanx= [tex]\sqrt{}1/2[/tex]
x= inverse. sin [tex]\sqrt{}1/2[/tex] is that how i get values for sin?
You will have two values, x2=a ⇒ x=±√a

Also if tanx=y, then x=tan-1(y). Where did you get inverse sine from?
 
You will have two values, x2=a ⇒ x=±√a

Also if tanx=y, then x=tan-1(y). Where did you get inverse sine from?
Exactly lol thats what i thought.. the question wants me to get sinx values if possible :9.
 

rock.freak667

Homework Helper
6,232
27
Exactly lol thats what i thought.. the question wants me to get sinx values if possible :9.
Sorry, I mis-read the question. While you can just find the values for x, and then find sinx.

You can also use tanx=sinx/cosx and then use cos2x=1-sin2x and solve for sinx.
 
ah k, thanks for helping me out :).
 

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