mica-lwe
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Can someone help with a(i) and a(ii) please? I don't really know where to start
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the bear
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for the acute angle you can make a right angled triangle using the numbers 3 & 5 as two of the sides. the third side can then be found using Pythagoras.
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tory88
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(Original post by mica-lwe)
Can someone help with a(i) and a(ii) please? I don't really know where to start
Can you draw a right angled triangle where you know two sides and one angle (alpha)?
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username1194059
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(Original post by mica-lwe)
Can someone help with a(i) and a(ii) please? I don't really know where to start
I believe you can assume that the angles in question are part of a right angle triangle. Therefore with Pythagoras' theorem you can work out the unknown side and thereby calculate Tan(alpha) and Tan(Beta).


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economicsrocks
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I think you have to draw two triangles with them and use the CAST diagram for the obtuse/acute information.

So: cos a is 3/5. Therefore, using triangles and Pythagoras (this would be easier if I could show you this by drawing it, sorry!), tan a is 3/4. Since cos a is acute, it is in the 'A' quadrant, so tan a is positive 3/4.

For aii) tan B is 1/root 3 (using triangles and Pythagoras) Since sin a is obtuse, it is in the 'S' quadrant on the CAST diagram, and tan B is therefore negative (-1/ root 3)

I hope this makes sense!
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mica-lwe
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Thankyou figured it out! Just needed a starting point
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mica-lwe
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(Original post by economicsrocks)
I think you have to draw two triangles with them and use the CAST diagram for the obtuse/acute information.

So: cos a is 3/5. Therefore, using triangles and Pythagoras (this would be easier if I could show you this by drawing it, sorry!), tan a is 3/4. Since cos a is acute, it is in the 'A' quadrant, so tan a is positive 3/4.

For aii) tan B is 1/root 3 (using triangles and Pythagoras) Since sin a is obtuse, it is in the 'S' quadrant on the CAST diagram, and tan B is therefore negative (-1/ root 3)

I hope this makes sense!
I have never heard of a CAST diagram:confused: is this the only way to work it out?
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economicsrocks
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(Original post by mica-lwe)
I have never heard of a CAST diagram:confused: is this the only way to work it out?
That's the method I learnt, but if you haven't been taught it don't worry This summarises it, if you were curious:
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Student20
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Just came across a similar question and this video tutorial really helped, worth checking out, runs through the CAST diagrams which I too never really knew before I watched it.

http://examsolutions.net/maths-revis...tutorial-2.php
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