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C2 trig question, confused!

Could someone explain step by step how to do this?

In triangle ABC, AB = Xcm, BC = (4 - X) cm, angle BAC = Y and angle BCA = 30 degrees. Given that sin Y degrees = 1/root 2, show that X = 4 (root 2 - 1)


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Original post by JodieW
Could someone explain step by step how to do this?

In triangle ABC, AB = Xcm, BC = (4 - X) cm, angle BAC = Y and angle BCA = 30 degrees. Given that sin Y degrees = 1/root 2, show that X = 4 (root 2 - 1)


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Step-by-step solutions are not permitted on the maths forum - you should post some working so that hints can be given.

If you can't see where to start, think about the sine rule.
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Robbie242
Original post by JodieW
Could someone explain step by step how to do this?

In triangle ABC, AB = Xcm, BC = (4 - X) cm, angle BAC = Y and angle BCA = 30 degrees. Given that sin Y degrees = 1/root 2, show that X = 4 (root 2 - 1)


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Draw a triangle then look at your rules of trig from the chapter you learned
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JodieW
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Original post by Farhan.Hanif93
Step-by-step solutions are not permitted on the maths forum - you should post some working so that hints can be given.

If you can't see where to start, think about the sine rule.


ImageUploadedByStudent Room1363966912.227643.jpg

This is what I've done so far. I don't know if it's right :/


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JodieW
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Original post by Robbie242
Draw a triangle then look at your rules of trig from the chapter you learned


I've done this so far but I just don't know how to continue to get X = 4(root 2 - 1)



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JodieW
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Original post by JodieW
I've done this so far but I just don't know how to continue to get X = 4(root 2 - 1)



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ImageUploadedByStudent Room1363967022.119163.jpg


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Reply 6
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Robbie242
Original post by JodieW
ImageUploadedByStudent Room1363966912.227643.jpg

This is what I've done so far. I don't know if it's right :/


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Rationalise the denominator and then bring all X's to one side and factorise leaving X outside. Then divide through by your factorisation and then rearrange some more
(edited 11 years ago)
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JodieW
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Original post by Robbie242
Rationalise the denominator and then bring all X's to one side and factorise leaving X outside. Then divide through by your factorisation and then rearrange some more


ImageUploadedByStudent Room1363967543.500890.jpg

Is this correct so far?


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Reply 8
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Robbie242
Original post by JodieW
ImageUploadedByStudent Room1363967543.500890.jpg

Is this correct so far?


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You times is by root 2 but in the end you'd still get the same product, so yeah divide through by 2, and then rearrange to have all X's on one side, then factorise and divide through by the bracket; from this point on you type it into your calculator rather then going for another round of rationalising
(edited 11 years ago)
Reply 9
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JodieW
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Original post by Robbie242
You times is by root 2 but in the end you'd still get the same product, so yeah divide through by 2, and then rearrange to have all X's on one side, then factorise and divide through by the bracket; from this point on you take type it into your calculator rather then going for another round of rationalising


I've done it now, thank you :smile: I'm so stupid ._.


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