Trig problem

[electrogeek]

Hello everyone. Please can I have some help with this problem? Thanks.

 

[Deleted member 4993]

View attachment 5371 Hello everyone. Please can I have some help with this problem? Thanks.

Hint: Use Law of Cosines.

What are your thoughts?

Please share your work with us ...even if you know it is wrong

If you are stuck at the beginning tell us and we'll start with the definitions.

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[electrogeek]

These are my workings so far. I forgot to say that I'm in year 11 at the moment. I know that there's something wrong but I can't find it anywhere.

 

[Deleted member 4993]

View attachment 5372 These are my workings so far. I forgot to say that I'm in year 11 at the moment. I know that there's something wrong but I can't find it anywhere.

4*7 = (2x+1)² + (2x-1)² - 2(2x+1)(2x-1)Cos(60°)

28 = 8x² + 2 - 2*(4x² - 1)* 1/2

28 = 4x² + 3

Continue......

 

[electrogeek]

so is x going to be 2.5?

 

[Deleted member 4993]

so is x going to be 2.5?

You should be able to check the answer by substituting the value of 'x' in the original problem!

 

[Steven G]

so is x going to be 2.5?

Quadratics can have up two solutions. Hint: x^2=9 has two solutions, NOT one.

 

[pka]

Quadratics can have up two solutions. Hint: x^2=9 has two solutions, NOT one.

While that is true, in this case a negative answer makes no sense.

 

[electrogeek]

Thank you everyone for the help. I think I just had a mental blank for some reason.