Respuesta :

Answer:

The value of Cos(60°) is ½

Step-by-step explanation:

B)as we know

b²=a²+c²-2ac.cos(b)

b=√5²+8²-2.5.8×cos(60°)

b=√25+64-80×½

b=√25+64-40

b=√89-40

b=√49

b=7 (proven)

We have to Prove b=7.

What is a Triangle?

A plane figure with three straight sides and three angles.

How to solve it?

As we know,

b²=a²+c²-2ac.cos(b)

b=√5²+8²-2.5.8×cos(60°)

b=√25+64-80×½

b=√25+64-40

b=√89-40

b=√49

b=7 (proven)

Learn more about Triangle:

https://brainly.com/question/17335144

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