# C4 question

Watch
Announcements
#1
Can someone help with a(i) and a(ii) please? I don't really know where to start
0
5 years ago
#2
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.
0
5 years ago
#3
(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)?
0
5 years ago
#4
(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).

Posted from TSR Mobile
0
5 years ago
#5
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!
0
#6
Thankyou figured it out! Just needed a starting point
0
#7
(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 is this the only way to work it out?
0
5 years ago
#8
(Original post by mica-lwe)
I have never heard of a CAST diagram 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:
1
5 years ago
#9
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
1
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### Should there be a new university admissions system that ditches predicted grades?

No, I think predicted grades should still be used to make offers (726)
33.81%
Yes, I like the idea of applying to uni after I received my grades (PQA) (920)
42.85%
Yes, I like the idea of receiving offers only after I receive my grades (PQO) (407)
18.96%
I think there is a better option than the ones suggested (let us know in the thread!) (94)
4.38%