Find the indicated trig function of

θ, if θ is an angle in standard position with the terminal side defined by the given

point.

(12, 16); Find cos θ.

answer is 4 over 5 but how do i find this?

please help :P

Printable View

- Oct 25th 2007, 05:30 PMHelpMePleaseFriendFind the indicated trig function PLZ HELP!Find the indicated trig function of

θ, if θ is an angle in standard position with the terminal side defined by the given

point.

(12, 16); Find cos θ.

answer is 4 over 5 but how do i find this?

please help :P - Oct 25th 2007, 05:39 PMDINOCALC09
(x,y) ---> (12,16) so 12 is your x value and 16 is your y value.

Plot this point on a unit circle and connect the center to the point. The angle from the horizontal x axis to the line is θ.

Have you ever learned SOHCAHTOA

since you are dealing with cos, you want to know that cos is adjacent/hypothesis.

In this instant, the hypothesis is the line you drew on the unit circle. To find it, we use the pathagorean theorem a^2 + b^2 = c^2.

12^2 + 16^2 = 400

take the square root to get c, which = 20

now is when we look back to cos = adjacent / hypothesis

the adjacent value is 16, while the hypothesis value is 20.

16/20 is your answer, but when you simplify (both have multiples of 4 so divide both the numerator and denominator by this)

AND AS YOU SAID...

your answer will be 4/5 - Oct 25th 2007, 05:55 PMHelpMePleaseFriendso if...
if the given numbers were lets say

(14,18)

i would do 14^2 = 196

18^2 = 324

= 520

then sqaure root of 520 = 22.8 ? i'd round to 23?

then fnd square root of 23 and 18

square root of 23 comes to 4.795 would i round to 4.8 or 5

square root of 18 = 4.24 so 4

answer would be 5 over 4?

nevermind that's wrong >_< i was doing square root. 23 is not divisable by anything >_< grrr i'm confused.

i understand going through the first one... but no this one. i just gave 23 and 18 as an example but it doesn't seem possible to do? - Oct 25th 2007, 06:18 PMqyzren
if you have (14,18)

then your hypotenuse will be ~22.80

i don't recommend rounding down at this point.

so your cos θ will be 18/22.80 ~ 0.789

Note: when using trig functions, for cos θ & sin θ it is not possible for it to be greater than 1 unless you're using imaginary numbers which i doubt you're doing.