trigonometry problems

C

christina18

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Apr 3, 2006
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Hello! I was just wondering if somebody can tell me if the following are correct. You guys really helped me before, so I'm coming back for more helpful assistance. Thanks so much!

1. Find sin A if cos A=8/9 and A is in quadrant IV.
a. -radical (17)/8
b. -radical (17)/9
c. -9/8
d. -raidcal (17)
*choice b

2. find the exact value of sin (-1050degrees).
a. radical (3)/2
b. radical 3
c. 1/2
d. radical (2)/2
choice A

3. using algebraic methods, find the exact value solutions in the interval [o,2pie) to the trig equation: 2cos x +4=3.
a. -1/2cos
b. Pie/6, 5pie/6
c. pie/3, 7pie/3
d. 2 pie/3, 4pie/3
e. no solution
*choice b
 
Cherry PIE is the all-American desert! It can be messy!
There is a number pi.
Is that what you mean in this posting?
 
no ... Pie is something you eat, as pka stated.

pi is the greek letter that represents the numerical ratio of the lengths of the circumference of a circle to its diameter.
 
1) Yes.
2) No.
3) No.

If you have questions, please reply showing your work. Thank you.

Eliz.
 
Those problems are really confusing, is there a way somebody can please show me how to begin it? I would show you my work but its not even close to being right.
thank you!
 
christina18 said:
I would show you my work but its not even close to being right.
Click to expand...
Please reply showing your work anyway. The tutors will be glad to help you find any errors.

Thank you.

Eliz.
 
for the 2nd one....I put sin(-1050 degrees) into my calculator and got 0.5...1/2 so choice C

for the 3rd one I'm getting choice c for an answer am I correct?
 
christina18 said:
for the 2nd one....I put sin(-1050 degrees) into my calculator and got 0.5...1/2 so choice C
that's not the idea ... start by adding multiples of 360 to -1050 until you get an angle that is coterminal with an angle between 0 and 360.
-1050 + 3(360) = 30 ... what is the value of sin(30)?

for the 3rd one I'm getting choice c for an answer am I correct?
no.
2cos(x) + 4 = 3
2cos(x) = -1
cos(x) = -1/2 ... now, at what angles between 0 and 2pi is the cosine -1/2?
if you don't know right off the top of your head, then i highly recommend you learn the unit circle
Click to expand...
 
Hmmm for number 2 you kinda lost me....1/2 isnt the correct one? The value of sin(30)=-0.988

for the 3rd one the answer is choice a -1/2cos
 
christina18 said:
Hmmm for number 2 you kinda lost me....1/2 isnt the correct one? The value of sin(30)=-0.988
change your calculator back to degree mode, sweetie.

for the 3rd one the answer is choice a -1/2cos
choice "a" makes no sense whatsoever ... did you even look at the link to the unit circle I provided? Jeez-Louise, LOOK at it!
Click to expand...
 
find the exact value of sin (-1050degrees).
a. radical (3)/2
b. radical 3
c. 1/2
d. radical (2)/2
choice C bc sin(30)=0.5...


using algebraic methods, find the exact value solutions in the interval [o,2pie) to the trig equation: 2cos x +4=3.
a. -1/2cos
b. Pie/6, 5pie/6
c. pie/3, 7pie/3
d. 2 pie/3, 4pie/3
e. no solution
*choice E
the angles that are between 0 and 2pi is the cosine -1/2 has 330 degrees=-30degrees
 
using algebraic methods, find the exact value solutions in the interval [o,2pie) to the trig equation: 2cos x +4=3.
a. -1/2cos
b. Pie/6, 5pie/6
c. pie/3, 7pie/3
d. 2 pie/3, 4pie/3
e. no solution
*choice E
the angles that are between 0 and 2pi is the cosine -1/2 has 330 degrees=-30degrees
Click to expand...

Methinks you have beaten this dead horse enough ... choice E is incorrect and you're running out of choices. If cosx = -1/2, and x is a value between 0 and 2pi,
then x = 2pi/3 or x = 4pi/3.
 
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