
William W. answered 06/22/21
Math and science made easy - learn from a retired engineer
Between 3π/2 and 2π (quadrant 4), a sketch would look like this:
because cos(θ) = adjacent/hypotenuse meaning we can draw the adjacent side as "4" units long and the hypotenuse as "9" units long. To find the other side of the triangle, use the Pythagorean Theorem:
42 + y2 = 92
16 + y2 = 81
y2 = 81 - 16
y2 = 65
y = √65
Now we can write the 6 trig functions:
cos(θ) = 4/9
sin(θ) = opp/hyp = √65/9
tan(θ) = opp/adj = √65/4
etc

Mark M.
Illustragive graphic!06/23/21