Question

If sin (B) = -1/2 with B in QIII, find cos (B/2).

Answer 1

if b is in Q3 of the plot, then that means that b must be 210 degrees. thus cos (210/2) is just cos(105) which is just about -1/4

Answer 2

I knew that it was cos105, but I tried typing in -1/4, and that is wrong.

Answer 3

In the calculator, it is -0.2588. A bit off of -1/4.