Trig help

[cobi]

I'm stuck on this question, I slightly remember this but got no idea where to start. Help Appreciated.

 

[Dr.Peterson]

I would start with the definition of trig functions in terms of a point (x,y) on the terminal ray in standard position: [MATH]\sin(\theta) = \frac{y}{r}[/MATH], [MATH]\cos(\theta) = \frac{x}{r}[/MATH], [MATH]\tan(\theta) = \frac{y}{x}[/MATH]. The negative cosine implies that [MATH]x < 0[/MATH]. Sketch the angle and look for relationships.

If you were familiar with identities (which is less likely if you "slightly remember" the topic), you could also use them.

Does this give you enough of a nudge?

 

[R.M.]

Tangent [MATH]\theta[/MATH] is positive, while cosine [MATH]\theta[/MATH] is negative. What quadrant is [MATH]\theta[/MATH]?

 

[cobi]

Well I did tan (θ) =y/x so tan (θ) =6/10
I then used Pythagoras to find r sqrt(6^2)+(10^2) which gave me 2sqrt34
So i then got sin (θ) = -6/2sqrt34

Is this is wrong, are you able to tell me where I went wrong

 

[Steven G]

Well done.

 

[cobi]

Well done.

thanks