# Thread: what is the angle of a triangle when tan = -1

1. ## what is the angle of a triangle when tan = -1

what is the angle of a right triangle when tan = -1? Any help is really appreciated

Edit: I solved it! Theta = 315 and 135 degrees!

BUT, now the problem is, when is sin an angle = -1 . I got angle = 270 degrees and ____________ (angle is greater than or equal to 0 and smaller or equal to 360 degrees)

2. ## Re: what is the angle of a triangle when tan = -1

Let your unknown angle be x and consider the domain $\displaystyle 0 \leq x \leq 360$ degrees. (otherwise we have an infinite amount of solutions)
For sin(x) = -1 there is only one solution, 270 degrees, on the domain I specified. If I didn't specify a domain the solution would be x + 360n, where n is an integer

Have you learned the unit circle?

3. ## Re: what is the angle of a triangle when tan = -1

Let your unknown angle be x and consider the domain $\displaystyle 0 \leq x \leq 360$ degrees. (otherwise we have an infinite amount of solutions)