Why does cos(t)=x and sin(t)=y?

Derivative of sin(x) and cos(x), PROOF

Where do Sin, Cos and Tan Actually Come From - Origins of Trigonometry - Part 1

Trigonometric Equation: Solve cos (x) - sin (x) = 0

Calculus Product Rule Example f(x) = sin(x)*cos(x)

Trig Help: Graphing y = sin x + cos x.

Proof that the Derivative of cos(x) is -sin(x) using the Limit Definition of the Derivative

Solve cos(x) - sin(x) = 1

sin(-x) = -sin(x). sin(x) is an odd function. cos(-x) = -cos(x) cos(x) is an even function.

Trigonometric Identity cosx + sin x = sq rt 2 cosx find cosx - sinx

Verify the Trigonometric Identity cos(pi/2 + x) = -sin(x)

sin(x) + cos(x) = 1 by Identities (Flawed)

sin(x)+cos(x)=sqrt(2) | Trigonometry

why sin(2x)=2sin(x)cos(x)

How to Solve cos(x) + sin(2x) = 0 (Trigonometric Equations)

Trigonometry Proof: cos (x + y) = cos x cos y – sin x sin y (https://youtu.be/b0o_dvFkYbU)

Why does sin(2x) = 2sin(x)cos(x)

Proof that the Derivative of sin(x) is cos(x) using the Limit Definition of the Derivative

Sin(90-A), Sin(90+A), Cos(180-A), Cos(180+A), Sin(270-A), Sin(270+A),Cos(360-A) How Why Trigonometry

lim x approaches 0: (1-cosx)/(sinx)