Given 90<theta<180, and cos(theta)=-5/13, what is sin(theta/2)
90°<θ<180°
cos θ =-5/13
sin(θ/2) = ±√(1-cosθ / 2) = √]1-(-5/13) / 2] = √(9/13)
note: θ/2 at 1st. Q, therefore we choose +
Comments
90°<θ<180°
cos θ =-5/13
sin(θ/2) = ±√(1-cosθ / 2) = √]1-(-5/13) / 2] = √(9/13)
note: θ/2 at 1st. Q, therefore we choose +