## HorribleAtMath Group Title for sin, cos, tan, csc, sec, and cot functions, how do you find the angles? 2 years ago 2 years ago

1. HorribleAtMath Group Title

i know you type in the calculator inverse sin..etc but like how do you know which quadrants they are in

2. y2o2 Group Title

the inverse functions $\sin^{-1} or \space \cos^{-1} or \tan^{-1}$ and so on

3. HorribleAtMath Group Title

i know that

4. HorribleAtMath Group Title

but how do you know which quadrant

5. HorribleAtMath Group Title

once you find that reference angle

6. y2o2 Group Title

Ah, ok i got it

7. Mertsj Group Title

Just remember that the cos is like x and the sin is like y. That gives you the sign of all the functions in all the quadrants.

8. HorribleAtMath Group Title

hmmm still sorta confused. can you give me an example mertsj?

9. y2o2 Group Title

you have to check the value of the function in the first quad. all functions are positive in the second quad. sine is the only positive the rest are negative in the third quad. tan is the only positive the rest are negative in the fourth quad. cosine is the only positive the rest are negative so when you find the angle , you can determine in which quad it is.

10. y2o2 Group Title

|dw:1332718026574:dw|

11. HorribleAtMath Group Title

ok so like if i have sin x = 1/2

12. Mertsj Group Title

|dw:1332717956955:dw|

13. HorribleAtMath Group Title

so if i have sin = 1/2 that means y= 1 and R = 2

14. HorribleAtMath Group Title

15. y2o2 Group Title

for example if sin(x) = 0.5 and x belongs to [0,180] then x must be in the first or the second quad. because it's +ve and sin^-1(0.5) = 30 so x =30 or x = (180-30 = 150)

16. y2o2 Group Title

sorry x belongs to [0,360]

17. HorribleAtMath Group Title

uhhhh..

18. HorribleAtMath Group Title

for sin3x = 1/2 why is the answer pi/18 and 5pi/18 ?

19. Mertsj Group Title

$3x= \frac{\pi}{6}, \frac{5\pi}{6}$ $x=\frac{\pi}{18}, \frac{5\pi}{18}$

20. HorribleAtMath Group Title

but why

21. Mertsj Group Title

3x=1/6 What is x?

22. HorribleAtMath Group Title

idk

23. Mertsj Group Title

|dw:1332719500565:dw|

24. Mertsj Group Title

|dw:1332719528422:dw|

25. HorribleAtMath Group Title

lol 1/18

26. Mertsj Group Title

|dw:1332719572812:dw|

27. precal Group Title

|dw:1332723649132:dw|

28. precal Group Title

This is how I remember it: All Students Take Calculus It helps you remember which functions are positive. Quadrant 1 : They are all positive