Question

Find the point on the terminal side of θ = -3pi/4 that has an x coordinate of -1. Show your work for full credit.

Answer 1

So to find the coordinate, we must find it's y-value. We have the x-value of the side lying on the x-axis and an angle that is made with the x-axis of pi/4, but how many units down do we go down, or what is the y-value? From SOHCAHTOA,, which should we use that deals with the y-value and uses the x-value?

Answer 2

@genius12 I know it's not tan that we use so Im thinking it's sine

Answer 3

@erickkoro, It is in-fact tan. What made you think it wasn't tan lol.

Answer 4

@genius12 because i thought we needed the hypotenuse. .

Answer 5

tan(x) = opposite/adjacent. We have adjacent side, we need the opposite side which we can solve for. Remember the coordinate (x, y) has two parts: the x-value and y-value. We know the x-value, so to find the y-value, we would have to use tangent.

Answer 6

@genius12 Alright, I'm with you so far .

Answer 7

@erickkoro You with me?

Answer 8

Can you solve for y?

Answer 9

@genius12 I see how you got everything but I would of never been able to come up with it by myself, & is y=-1 ?

Answer 10

That is right.

Answer 11

@erickkoro, you see, once you do enough problems and get familiar with the concepts, you will automatically recognise the situation and what needs to be done. For now I suggest you strengthen your trig skills by understanding SOHCAHTOA, and do similar problems. Also look at the unit circle and the common trig ratios.

Answer 12

@genius12 so is -1 the point on the terminal side of θ = -3pi/4 ?

Answer 13

@genius12 ?

Answer 14

@erickkbro sorry was afk. that is correct, the point joining the terminal side of the angle has an x-coordinate of -1.