trig question: if cos(theta)=1/9, theta acute, then find....

G

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I need some help getting through this question. Any help is appreciated.

If Θ is an acute angle with cosΘ=1/9, find the exact value of sin a/2
 
That's pretty tricky, since there is no given relationship between 'Θ' and 'a'.

Assuming you meant "sin(Θ/2)"

Draw a right triangle.
Lable an acute Angle 'Θ'
Label two sides of the triangle so that cos(Θ) = 1/9
Use the Pythagorean Theorem to calculate the third side.

That was just for practice. Just use the formula \(\displaystyle \L\,sin(\frac{\Theta}{2}) = \sqrt{\frac{1-cos(\Theta)}{2}}\)
 
I am not sure is I used the right character for "a" It should be the leter for alpha
 
aroot said:
I am not sure is I used the right character for "a" It should be the leter for alpha
Click to expand...
What is the relationship between theta and alpha? (Keep in mind that we can't see whatever pictures you're looking at.)

Thank you.

Eliz.
 
There is no picture with the question. It only says that if theta is an acute angle. maybe that is why I can't figure it out. I do have the possible answers if it would help show what they are wanting me to accomplish.

a. 1/3
b. 2/3
c. sqrt3/3
d. sqrt5/3
 
I still can't really say, since we still don't really have a rational problem statement.

I'd go with 'b', if I had to.
 
If there is no relationship given between theta and alpha, then there is no way to answer.

You might want to point this out to your instructor. It might be a known typo.

Good luck!

Eliz.
 
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