### I'm the scribe today

Sorry I took so long.The first thing that we did today was correct the worksheet from yesterday. Then we learned about the cosine law the sub teacher said no matter what question you get you never use the ''cosine law'' more than once in the same question. The ''cosine law '' is used when you only two sides and an angle or when you know the sides of the triangle. The formula for the cosine law is a squared = b squared+ c squared- 2bc cosA or b squared = a squared + c squared- 2ac cosB It depends on the letters that your given. An example: Triangle DEF with d=9, e=16,f=21 Find angle F

f squared= e squared+ d squared-2ed cosF

f squared= e squared+ d squared-2ed cosF

21 squared=16squared+ 9 squared-2(16)(9) cosF

21 squared-16 squared-9 squared=-2(16)(9)cosF

(21 squared-16 squared-9 squared) = -2(16)(9)cosF

divided by -2(16)(9) divided by -2(16)(9)

=441-81-256 = cosFdivided by -2(16)(9)

= -0.3611=cosF

arc cos

angleF=111 degrees

Then you find the other angles by using the sine law well that's the cosine law.

The home work for to night is ex.25(omit 8,11-15) and the two worksheets that we got both sides.

And the scribe for tomorrow is Janet hurray:)

## 1 Comments:

:o you are mean . lol

Post a Comment

## Links to this post:

Create a Link

<< Home