IXL - Law of Cosines (Precalculus practice)

Find

124°

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

ref_doc_title.

Learn with an example

question

Find

86°

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

86°

169

144

–

312

cos

86°

169

144

–

312

0.069…

291.235…

17.065…

To the nearest tenth,

≈

17.1

Looking for more? Try this:

$Confetti$

Excellent!

Now entering the Challenge Zone—are you ready?

Questions
answeredQuestions

Time
elapsedTime

hr	min	sec
00	00	04

SmartScore
out of 100
IXL's SmartScore is a dynamic measure of progress towards mastery, rather than a percentage grade. It tracks your skill level as you tackle progressively more difficult questions. Consistently answer questions correctly to reach excellence (90), or conquer the Challenge Zone to achieve mastery (100)! Learn more

Teacher tools

Work it out

Not feeling ready yet? These can help:

R.10Inverses of trigonometric functions using a calculator

II.10Find trigonometric functions using a calculator

Excellent! You got that right!

Jumping to level 1 of 1

Excellent!