Precalculus with Limits: A Graphing Approach, Sixth Edition
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Precalculus with Limits: A Graphing Approach, Sixth Edition View details
4. Trigonometric Functions of Any Angle
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Exercise 1 Page 289

Recall the definitions of trigonometric functions of any angle.

y/r

We are asked to fill in the blank in the following formula. sin θ = To do so, we need to recall the definitions of trigonometric functions of any angle. Let θ be an angle in standard position with (x, y) a point on the terminal side of θ and r=sqrt(x^2+y^2)≠ 0.

Then, we can find the values of all six trigonometric functions using the following formulas.

Definitions of Trigonometric Functions of Any Angle
sin θ = y/r cos θ = x/r
tan θ = y/x, x ≠ 0 cot θ = x/y, y ≠ 0
sec θ = r/x, x ≠ 0 csc θ = r/y, y ≠ 0

Let's take a closer look at the table and find the formula containing the expression sin θ.

Definitions of Trigonometric Functions of Any Angle
sin θ = y/r cos θ = x/r
tan θ = y/x, x ≠ 0 cot θ = x/y, y ≠ 0
sec θ = r/x, x ≠ 0 csc θ = r/y, y ≠ 0

According to the table, sin θ = yr. With this in mind, let's fill in the blank. sin θ = yr