Question

0

Answer 1

Do you know what quadrant that is in?

Answer 2

So theta is negative what angle?

Answer 3

315?

Answer 4

In radians. Hint: there are 2pi radians in the unit circle.

Answer 5

7/4

Answer 6

Hm.. I don't seem to be getting my point across. 7pi/4 is short of being all the way around the circle by 2pi - 7pi/4 radians. So it is the same as - pi/4 radians.

So do you know the values for pi/4 radians in the first quadrant?

Answer 7

45 degrees.

Answer 8

Yes. But do you know sin(pi/4) and cos(pi/4) }pi/4 = 45 degrees}

Answer 9

no? can u explain?

Answer 10

Here is the situation. The values you are looking for are sin, cos, and tan of 7pi/4. Well the numerical values are the same as for pi/4 (or 45 degrees) but you have to adjust the signs (positive or negative).

Answer 11

but these are my answer choices
sin Θ = negative square root 2 over 2; cos Θ = negative square root 2 over 2; tan Θ = 1

sin Θ = negative square root 2 over 2; cos Θ = square root 2 over 2; tan Θ = 1

sin Θ = square root 2 over 2; cos Θ = negative square root 2 over 2 tan Θ = -1

sin Θ = negative square root 2 over 2; cos Θ = square root 2 over 2; tan Θ = -1

Answer 12

Okay. So you know the numerical values already and all you have to find are the signs.

All of the signs of cos, sin, and tan are positive in the first quadrant. But you are in the fourth quadrant. So in the 4th quadrant is cosine positive or negative?

Answer 13

idk

Answer 14

Have you ever seen the unit circle?

Answer 15

yes.

Answer 16

Okay cosine is the length adjacent to the angle. It is positive in the first quadrant. What happens to it in the fourth quadrant?

Answer 17

it becomes negative.

Answer 18

@LarsEighner

Answer 19

am i that hopeless?

Answer 20

Nope. cos is an x value. In the first quadrant it is the same as in the fourth quadrant. I suppose it is pointless to ask about sin at this point. It is a y value, and in the 4th quadrant all the y-values are negative.

But we willl try one more. tan is sin/cos. It is positive in the first quadrant because both sin and cos are positive. But in the forth quadrant, sin is negative and cos is still positive, so what is the sign on tan?

Answer 21

negative.

Answer 22

Right. and I reckon thats a wrap.

sin Θ = negative square root 2 over 2; cos Θ = square root 2 over 2; tan Θ = -1

Answer 23

thank you soo much!!

Answer 24

The moral of this story is if you are wiley you never have to learn values outside the 1st quadrant, but you have to learn some way to remember what the signs are. The unit circle does it for me, but some people make up different mnemonics.