Math Is Fun Forum
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#1 2013-05-16 20:38:02
Trig
Solve: cot 18 cot 39 cot 51 cot 60 cot 72
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.
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#2 2013-05-16 22:05:24
- Bob
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- Registered: 2010-06-20
- Posts: 10,645
Re: Trig
hi Agnishom,
You might make a start using
Note: 18 + 72 = 90 and 39 + 51 = 90 so pairing the cots, writing as cos/sin and applying the above should simplify a lot.
cot 60 should be straight forward.
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob 
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#3 2013-05-16 22:30:09
Re: Trig
how would I work out cos(18-72)?
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.
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#4 2013-05-16 22:33:57
- Bob
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- Registered: 2010-06-20
- Posts: 10,645
Re: Trig
= cos 54
So simplify as much as you can eg. sin 90 = 1 etc
I'll try to see what happens next.
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#5 2013-05-16 23:06:51
- Bob
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- Registered: 2010-06-20
- Posts: 10,645
Re: Trig
Tried it. No sin90 at all just lots of cos90 = 0
So loads cancels and what is left cancels too.
It comes down to a single cot that you should know.
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#6 2013-05-16 23:27:31
Re: Trig
cot 60 = 1/root 3
Is it?
Please show me those simplifications 
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.
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#7 2013-05-16 23:39:33
- Bob
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- Registered: 2010-06-20
- Posts: 10,645
Re: Trig
yes that's it
etc.
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#8 2013-05-17 00:08:39
Re: Trig
Whee! Thanks a lot!
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.
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#9 2013-05-17 00:44:23
- Bob
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- Registered: 2010-06-20
- Posts: 10,645
Re: Trig
OR
I am embarrassed that I didn't spot this until just now. 
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#10 2013-05-17 01:02:38
Re: Trig
I am not sure how that would help
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.
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#11 2013-05-17 01:15:29
- Bob
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- Registered: 2010-06-20
- Posts: 10,645
Re: Trig
Well you could write
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#12 2013-05-17 01:42:52
Re: Trig
yeah, cool
I am afraid of trig
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.
Offline
#13 2013-05-17 05:26:58
- Bob
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- Registered: 2010-06-20
- Posts: 10,645
Re: Trig
hi
I was going to try to cheer you up with a joke, so I googled images for "afraid of trig". I was expecting some suitably horrid cartoon image of a trig monster.
What I got is shown below. I don't know whether to laugh or cry.
Bob
Children are not defined by school ...........The Fonz
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you! …………….Bob
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#14 2013-05-17 13:37:48
Re: Trig
Yes, its funny! (As I am not sure what it means) 
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
I'm not crazy, my mother had me tested.
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