IXL - Find trigonometric functions of special angles (Geometry practice)

Evaluate. Write your answer in simplified, rationalized form. Do not round.

cos

30°

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Learn with an example

question

Evaluate. Write your answer in simplified, rationalized form. Do not round.

cos

30°

key idea

The cosine

(

cos

)

of an angle in a right triangle is a ratio. It is the length of the adjacent leg

(

adj

)

divided by the length of the hypotenuse

(

hyp

)

The adjacent leg is the leg next to the specified angle and the hypotenuse is the side across from the right angle.

cos

(

)

adj

hyp

solution

To calculate

cos

30°

draw a right triangle with a 30° angle. This is a 30°-60°-90° triangle, which is a special right triangle. Its side lengths are

1, and 2.

30°

Now, calculate

cos

30°

The length of the adjacent leg is

and the length of the hypotenuse is 2.

cos

30°

Definition of cosine

adj

hyp

Definition of cosine

Plug in

adj

and

hyp

Plug in

adj

and

hyp

So,

cos

30°

Looking for more? Try these:

Lesson: Trigonometric ratios

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Not feeling ready yet? These can help:

Q.5Special right triangles

Q.2Trigonometric ratios with radicals: sin, cos, and tan

Q.3Trigonometric ratios: csc, sec, and cot

Lesson: Trigonometric ratios

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