Question

What are the sine, cosine, and tangent of Θ = 3 pi over 4 radians?

Answer 1

Notice the "x" and "y" coordinates

the x-coordinate is well, the cosine value
the y-coordinate is well, the sine value

now the tangent

$\bf tan(\theta)=\cfrac{opposite}{adjacent}=\cfrac{y}{x}\\\\ -------------------------------\\\\ tan(\theta )=\cfrac{\frac{\sqrt{2}}{2}}{-\frac{\sqrt{2}}{2}}\implies tan(\theta )=-1$