IXL - Law of Cosines (Algebra 2 practice)

Find

25°

Write your answer as an integer or as a decimal rounded to the nearest tenth.

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Learn with an example

question

Find

32°

Write your answer as an integer or as a decimal rounded to the nearest tenth.

key idea

The Law of Cosines states

a
2
=
b
2
+
c
2
–
2
b
c
cos
(
A
)
b
2
=
a
2
+
c
2
–
2
a
c
cos
(
B
)
c
2
=
a
2
+
b
2
–
2
a
b
cos
(
C
)

where each lowercase letter (like

)

is the length of the side opposite the vertex labeled with the same capital letter (like

If you know the lengths of two sides and the measure of the included angle (like

and

∠

you can use the Law of Cosines to solve for the length of the third side (like

solution

Since you know the lengths of two sides and the measure of the included angle

(

and

∠

use the Law of Cosines to find

the length of the remaining side.

–

cos

(

)

–

cos

32°

289

169

–

442

cos

32°

289

169

–

442

0.848…

83.162…

9.119…

To the nearest tenth,

≈

9.1

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II.12Inverses of sin, cos, and tan: radians

II.10Find trigonometric functions using a calculator

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