Question

Find the point on the terminal side of θ = pi/4 that has an x coordinate of 2.

Answer 1

(2,y)

Answer 2

It may help to draw a picture

Answer 3

I don't know how to do this without the hypotenuse

Answer 4

use the trig identity

tan(angle) = opposite/adjacent

tan(pi/4) = y/2

Answer 5

Do I have to make tan(pi/4) into degrees? Sorry for my confusion!

Answer 6

its ok, make sure you're in radian mode

Answer 7

do you have a calculator with you?

Answer 8

http://my.hrw.com/math06_07/nsmedia/tools/Graph_Calculator/graphCalc.html this is what I have

Answer 9

ok, make sure the radio button "Rad" is selected

Answer 10

ok

Answer 11

unfortunately, this only supports graphs, but you can still use this as a scientific calculator

type in what you see attached

Answer 12

notice how the y coordinate of each point is 1

Answer 13

so this means tan(pi/4) = 1

Answer 14

okay so y would be 2 because 1=y/2 is y=2 right?

Answer 15

you are 100% correct

Answer 16

yes! Thank you so much! I thought the line on the calculator meant nothing! :-) Thanks again!

Answer 17

you're welcome, the calculator is good for graphing, but it may be a bit clunky for other things (like simple arithmetic)

That's why I recommend using graph calc (which is what I use)

http://www.graphcalc.com/

Answer 18

Thanks so much! :) and I have one question, how did you know to use tan?

Answer 19

Because tangent deals with the opposite and adjacent sides

The opposite side is 'y' in this case. The adjacent side is 2 in this case.

Answer 20

Oh that makes total sense! Thanks again!

Answer 21

Use the mnemonic:

SOH
CAH
TOA


SOH: Sine - Opposite over Hypotenuse
CAH: Cosine - Adjacent over Hypotenuse
TOA: Tangent - Opposite over Adjacent

And you can pronounce it in your mind as "soak-a-toe-ah"

Answer 22

Cool thank you!

Answer 23

yw