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Maths year 11

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Original post by z_o_e
Wait. I can't use trigonometry here to find the angle as it isn't a right angled triangle?



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You still use trigonometry, using trigonometry doesn't mean it has to be a right-angled triangle. You use the cosine rule here, and cosine is a trigonometric function.
Reply 1541
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Original post by RDKGames
You still use trigonometry, using trigonometry doesn't mean it has to be a right-angled triangle. You use the cosine rule here, and cosine is a trigonometric function.


But I don't know how to find an angle using the trigonometry?

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Original post by z_o_e
But I don't know how to find an angle using the trigonometry?

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Start with the formula, label the wanted angle as whatever you want, and write out the things you know from that triangle.
Reply 1543
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Original post by RDKGames
Start with the formula, label the wanted angle as whatever you want, and write out the things you know from that triangle.


I don't get that. Because that formulae is for missing sides of a triangle?

And this has all its sides...

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Original post by z_o_e
I don't get that. Because that formulae is for missing sides of a triangle?

And this has all its sides...

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The cosine rule can be used to work out the angle as well by rearranging it for cosine. Just write out the info first of what you know.
Reply 1545
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Original post by RDKGames
The cosine rule can be used to work out the angle as well by rearranging it for cosine. Just write out the info first of what you know.




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Original post by z_o_e


Now plug it through the cosine rule with an unknown angle.
Reply 1547
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Original post by RDKGames
Now plug it through the cosine rule with an unknown angle.




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Original post by z_o_e


That's correct. Now you can do the inverse cosine of both sides for the angle.
Reply 1549
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Original post by RDKGames
That's correct. Now you can do the inverse cosine of both sides for the angle.


Didn't get that..



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Original post by z_o_e
Didn't get that..



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Try again. You entered something on your calculator wrong then.
Reply 1551
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Original post by RDKGames
Try again. You entered something on your calculator wrong then.




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Original post by z_o_e


Correct :smile:

But angles aren't measured in centimetres.
Reply 1553
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Original post by RDKGames
Correct :smile:

But angles aren't measured in centimetres.


Woowowe thank you ♥

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Original post by z_o_e
Woowowe thank you ♥

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asdfasdas.PNG
Reply 1555
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Original post by RDKGames
asdfasdas.PNG


So question one is asking for the angles of a and b added up?

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Original post by z_o_e
So question one is asking for the angles of a and b added up?

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No. This is a recurring misinterpretation for you. Angle ABC means the angle created by the lines AB and BC.

A, B and C are vertices of the polygon, they are not angles.
Reply 1557
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Original post by RDKGames
No. This is a recurring misinterpretation for you. Angle ABC means the angle created by the lines AB and BC.

A, B and C are vertices of the polygon, they are not angles.


So what am I suppose to find?

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Original post by z_o_e
So what am I suppose to find?

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The acute angle at B.
Reply 1559
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Original post by RDKGames
The acute angle at B.


I don't think I'm ready for this question just yet. Maybe tomorrow? I can't understand these questions for some REASON ABC

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