now let's go back to the unit circle in the unit circle we said that it's a circle that has a radius of one so if we were to draw a triangle the hypotenuse of the triangle will have a value of 1 because that's the radius that's the distance between the center of the circle and a point on a circle now this is x and this is y and on the inside we have the angle theta now let's see if that angle corresponds to an angle of 45 degrees well actually let's make it 30. let's say theta is 30. so that would correspond to a point of root 3 over 2 that's the x value and the y value would be one half now we said that sine of theta when we have a unit circle and keep in mind this will be true when r is one if r is not one the equation will change which we'll talk about later but for a unit circle sine theta is simply y so in this case sine 30 is the y coordinate one half cosine theta we said it's x now there are some other trigonometric functions they need to know there's six of them these are the first two tangent theta is sine divided by cosine so tangent theta is y divided by x cosecant theta is one over y and secant theta is one over x cotangent theta is x divided by y so those are the six trigonometric functions that you need to be aware of