Thread: 3 pretty easy questions

1.)



2.)


3.)

Originally Posted by stiitches

[3 images]

This looks a lot like you asking us to do your homework for you. What have you tried? Where are you stuck?

For the third one I did

1/(5/4) since cos=1/sec
so its cos(y)=4/5
then did cos(2y)=8/5
but it was wrong

for the other two, not sure how to start them and what the Qs are exactly asking.

Originally Posted by stiitches

For the third one I did

1/(5/4) since cos=1/sec
so its cos(y)=4/5
then did cos(2y)=8/5
but it was wrong

for the other two, not sure how to start them and what the Qs are exactly asking.

Thanks.

Q3, it's right that cos(y)=4/5, but the next step is not right because it's not generally true that cos(2*theta) = 2*cos(theta).

Use identity

Q1 You need to know interval notation to see what form the answer is supposed to be in. And as for getting the answer you can do:









Factor the quadratic and see where the inequality holds.

Q2 asks you to find some trig function values based on a single given value. You need some trig identities. One such is that . Can you continue?

Originally Posted by stiitches

1.)

and a product of numbers is positive if and only if an even number of its factors are negative.

2.)

csc is defined as "hypotenuse over opposite side" so you can imagine a right triangle with one vertex at (0, 0) on a coordinate system, right angle at (3, 0) and hypotenus of length 5. Where is the third vertex?

3.)

cos(2y)= cos^2(y)- sin^2(y). You are told what sin(y) is and, of course, cos(y)= 1/sec(y).