Cosine

Law of cosine

SAS OR SSS

Geometry book

Module 14

Lesson 14.2

Law of cosine

• Pages (756 - 761)

Objectives :             G-SRT.D.10

1- Use the law of cosine to solve the triangle ( Find the unknown measures ) . 

Multiple Choice

If you know SSA from the triangle which way you will use to find the missing measures ?

• LAW OF SINES

• LAW OF COSINES

Multiple Choice

If you know SAS from the triangle which way you will use to find the missing measures ?

• LAW OF SINES

• LAW OF COSINES

For △ABC, the Law of Cosines states

that: 

a²= b²+ c² -2bc cos⁡A

b²= a²+ c² -2ac cos⁡B

c²= b²+ a² -2ba cos⁡C

Multiple Choice

Page 762:

14. a = 5, b = 8, c = 6

Find m< B ?

• 87.13⁰

• 93⁰

• 80⁰

• 87⁰

Page 756:

Solve △ABC. Round intermediate results to 3 decimal places and final answers to 1 decimal place.

1- Find the measure of the largest angle, ∠C :

Page 756:

Solve △ABC. Round intermediate results to 3 decimal places and final answers to 1 decimal place.

1- Find the measure of the m ∠A :

Multiple Choice

page 760:

which law of cosine you will use to find p ?

• p²= r²+ q² -2rq cos⁡P

• r²= p²+ q² -2pq cosR

• q²= r²+ p² -2rq cos⁡Q

Multiple Choice

page 760:

which law of cosine you will use to find m<R ?

• p²= r²+ q² -2rq cos⁡P

• r²= p²+ q² -2pq cosR

• q²= r²+ p² -2rq cos⁡Q

Multiple Choice

page 760:

which law of cosine you will use to find m<Q ?

• p²= r²+ q² -2rq cos⁡P =?

• r²= p²+ q² -2pq cosR =?

• q²= r²+ p² -2rq cos⁡Q = ?