# math

There are no typos and no work b/c I don't know how to do them. Thanks.

1)Find cos theta if sin theta=3/5 and 90 degrees<theta<180 degrees.
A)4/5
B)-4/5
C)square root of 34/5
D)-square root of 34/5
I chose A

2)Simplify:1-csc^2theta/cot^2theta
A)-1
B)1
C)tan^2theta
D)1/sin^4theta
I chose A

3)Simplify:-5(cot^2theta-csc^2theta)
A)5
B)-5
C)-5csc^2 theta
D)5csc^2 theta
I chose B

4)Which expression is not equivalent to 1?
A)sin^2theta+cot^2thetasin^2theta
B)sin^2theta/1-costheta -1
C)sec^2theta+tan^2theta
D)cot^2thetasin^2theta/cos^2theta
I chose C

5)Which expression is equivalent to tan theta-sec theta/sin theta?
A)-cot theta
B)cot theta
C)tan theta-cot theta
D)tan theta-sec^2theta
I don't know

6)Find the exact value of cos375 degrees.
A)square root of 6 - square root of 2 over 4
B)square root of 6 + square root of 2 over 4
C)square root of 2 - square root of 6 over 4
D)- square root of 2 - square root of 6 over 4
I chose B

Work for #1

1)Find cos theta if sin theta=3/5 and 90 degrees<theta<180 degrees.
A)4/5
B)-4/5
C)square root of 34/5
D)-square root of 34/5
I chose A

cos^2theta+sin^2theta=1
cos^2theta=1-sin^2theta
cos^2theta=1-(3/5)^2
cos^2theta=1-9/25
cos^2theta=16/25
=4/5

thats the only one that I can show work for.

1. 👍
2. 👎
3. 👁
1. 6. First of all, cos 375 = cos 15
Use the formula for cos (A - B), with A = 60 degrees and b = 45 degrees. If you don't know it, look it up.

You will need to use the facts that
cos 45 = sin 45 = (sqrt2)/2
cos 60 = 1/2
sin 60 = (sqrt 3)/2

1. 👍
2. 👎
2. We have this:

(3) Simplify:

-5(cot^2theta-csc^2theta)

A)5
B)-5
C)-5csc^2 theta
D)5csc^2 theta

I chose A

You said B, right?

Let's see if that's true.

I will use x in place of theta to avoid having to write the word theta through and through.

So, x = theta.

cot^2 (x) = cos^2 (x)/sin^2 (x)

csc^2 (x) = 1/sin^2 (x)

We now have this:

-5(cos^2 (x)/sin^2 (x) - 1/sin^2(x) =

The trig terms within the parentheses become (-sin^2(x)/sin^2(x)) = -1

We now have:

-5 (-1) = 5

I say the answer is choice A for question 3.

I hope this helps.

To solve the rest, use the equivalent trig identities. You can find the rest of the trig identities through an online search.

Done!

1. 👍
2. 👎
3. #6)cos 375 = cos(60+45)
= cos 60 cos 45 - sin 60 sin 45
= 1/2 x sqrt 2/2 - sqrt 3/2 x sqrt 2/2
= sqrt 2 -sqrt 6/4 which is C? If so, I understand how we got it. Thank you for helping me

1. 👍
2. 👎
4. Surely you meant to write cos 375 = cos 15
= cos (60 - 45)

1. 👍
2. 👎
5. in my book its the same problem except its -3/5 and in my question its 3/5, so that would mean the final answer is 4/5 instead of -4/5 right?

1. 👍
2. 👎
6. drwls, Thursday, February 14, 2008 at 5:24pm
Surely you meant to write cos 375 = cos 15
= cos (60 - 45)

No, I meant to write +

1. 👍
2. 👎
7. thats how the formula is in my book but I see where you're coming from

1. 👍
2. 👎
8. 60 + 45 is not 15

1. 👍
2. 👎

## Similar Questions

1. to be a great asset to your company which of the following should you do? a. always look like you're working hard b. be a problem-solver c. be quiet and keep your eyes open d. be friendly with your boss**** 2. When you are

3. ### Latin (GA Connections Academy)

Can you please help me with these translations? I know this is just homework help and not "we're going to solve your problems" but I have been slaving over these problems for hours and yes I have cried. I have scoured every

4. ### General Physics I

A 50-N force acts on a 2-kg crate that starts from rest. When the force has been acting for 2 s the rate at which it is doing work is: I found this question online so I saw the answer is 2500 Watts. What I don't understand is how

1. ### Algebra

In six years Jill will be twice as old as Amanda. One year ago Jill was nine times older than Amanda. How old is Jill now? I tried 6 + 2x = x because in six years Jill will be twice Amanda's age, but this doesn't work. I need a

2. ### PHySics

A 1.63 nF parallel-plate capacitor is charged to an initial potential difference ΔVi = 100 V and then isolated. The dielectric material between the plates is mica, with a dielectric constant of 5.00. (a) How much work is required

3. ### Math

if f(x) = 2x^2+4 and g(x)=x-3 which number satisfies f(x)= (f o g)(x) A) 3/2 B) 3/4 C) 5 D) 4 I am positive that answer A is correct, i just cant get the work to prove it, i can disprove all other answers and my teacher has

4. ### Math (Help!)

Note: Remember to show all of the steps that you use to solve the problem. Be sure to use the text box where the question mark (?) first appears to show your mathematical work. you can use the comments field to explain your work.

1. ### math

suppose x S f(t) dt= x^2 - 2x + 1. Find f(x). 1 S = integral and 1 = lower level, x = upper i don't understand what i'm supposed to find/what to do and i didn't make any typos.

2. ### economics

Does Marx's essay help illuminate any of your own work experiences? Can you relate to his discussion? Why or why not? what if i don't have any work expericence could i just said that or is it talking about another work

3. ### Educational Tech

Which of the following terms is described as "the art and design of using text." A) Typography B) Elements of Design C) Typos D) Graphic Design My answer is A.

4. ### chemistry

what is the oxidation number for nitrogen in the following? NH3 NO2 1- N2 NO2Cl N2H4 We will be happy to critique your thinking or work. I don't even have a clue as to how to work it out.