NEW Beginner's Trigonometry Identities Problem

[courtbits]

Alright. I am sort of understanding this section on my online math lesson, but I am still struggling with it. Would be gladly appreciated if someone could help me with this:

If cosΘ = -4/9 with Θ in Quadrant II, find sinΘ

 

[MarkFL]

I want to ask you 2 questions:

• What is the sign of the sine function in Quadrant II?
• Is there an identity that can relate sine and cosine, that is, sine and cosine are the only two trig. functions present in the identity?

 

[courtbits]

I want to ask you 2 questions:

• What is the sign of the sine function in Quadrant II?
• Is there an identity that can relate sine and cosine, that is, sine and cosine are the only two trig. functions present in the identity?

1) I have no idea what you are asking. v~v <== Dunce
2) Umm.. $${sin}^{2}\theta + {cos}^{2}\theta = 1$$ ...I think. o-o"

YAAS. I figured out how to use the Latex stuff. :D

 

[MarkFL]

1) I have no idea what you are asking. v~v <== Dunce
2) Umm.. $${sin}^{2}\theta + {cos}^{2}\theta = 1$$ ...I think. o-o"

YAAS. I figured out how to use the Latex stuff. :D

1.) Picture the unit circle, and a point on the circle in Quadrant II...is the $y$-coordinate positive or negative?

2.) Yes, good...since you are being asked to find the sine function, can you solve this identity for $\sin(\theta)$? And then the answer to part 1.) will tell you which root to take.

3.) Good job using $\LaTeX$. One suggestion...precede the trig. functions with a backslash, and they will not be italicized which makes them look like string of variables rather than pre-defined functions. For example, the code:

\sin^2(\theta)+\cos^2(\theta)=1

produces:

$\sin^2(\theta)+\cos^2(\theta)=1$

Also, for clarity, it is always a good idea to enclose the arguments of the functions in bracketing symbols...this way everyone knows exactly what the angle is. :D