Trigonometryish question

[kaebun]

actully its more that im realy confused on how to find the sin , cos , tan etc. without a calculater i have a quiz tomarow and i am so confused... i get the basic ones like the sin(30) but i am confused about sin(-135) and ones that don't go with the unit circle, i don't understand how to do it in your head.

 

[jaggtagg7]

-135 is on the unit circle... notice its 90+45, making it a 45 degree, and the sin(45) is sqrt(2)/2

edit: i assume since you know sin(30) that you have studied the unit circle..

 

[Gene]

I would approach it as
sin(-135) =
-sin(135) =
-sin(90+45) =
-cos(45)

 

[kaebun]

thank you that makes sense