Our mission is to work out what theta in stage no.
1 and then stage no.
2 is find the total bearing, so let me walk you through it now as we do it.
So let us work out with the first stage, we want to work out what this angle here is,
now if you look at that it is a right angle triangle as you can see we have theta and
what we have 2 length now opposite or right in front 4 and around here next to it the
6, so the 6 it is adjacent is in it?
So opposite over adjacent now you remember what opposite over adjacent is?
Right?
So here is our opposite and here is our ADJ-- ok that is clearly going to be not as you
know not a sin, it is not a cos it is a tan.
So let me put this out, so we have—tan theta = now what is opposite?
Opposite is 4 --- all over adjacent right there see that?
That is the 6.
Okay let us divide by the four by the 6 or change the fraction in to a decimal, it is
going to take tan theta = 4/6 it is going to be a very long decimal it is 0.6666 and
a little dot up there means goes infinity, goes forever indefinitely.
So now let us go to the calculator and do an inverse of shift, shift tan theta will
give you, theta by itself – and that will be 33 degrees and 41 minutes.
Now 33 degrees 41 minutes we want to the nearest degree so can round this up, can’t we?
Why do we go up?
Because see that 41?
It is actually means that is more than 30 minutes, now 30 is the magic marker, that
is 41 is above 30 which means we round that up, we go up so that becomes theta = 34 degrees
so that is theta right in there and that is to the nearest degrees.
Now our mission is to work out what is the total bearing, so that is step no. 2.So The
total bearing is always from through north which is vertical like that sweeping horizontal
like that to your right sweeping all the way down to there so in order for us to work the
total amount we got to add this little angle here.
Now that is the right is in it?
always between north and east, north and west and it is always 90 degrees so we can safely
put 90 degrees there so let me just mark that out – ok there is our marker there 90 degrees.
So the total bearing of C from A sweeps around all the way see that yellow down to there
so we need to add this which is of course – that angle there is 90 degrees.
ok so all we got to do add the theta with the 90 and we have the total bearing of C
from A. so let us do that ok, let us start of, bearing—of C from A—and another way
to write that C from A, AC – that = -- theta -- + 9 0 degrees, so let us put in the magic
amount – so the bearing AC = now theta we know is 34 degrees – and that comes right
over here that we worked out earlier plus 90 degrees – adding the 2 together – 34
+ 90 is going to give us the total bearing from thru north all the way there down to
C is – and that T indicated from through north – 124
degrees
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Take a minute to check out our website at http://www.vividmaths.com.
You will find additional resources, cheat sheets, transcripts and other math videos
that are not available on Youtube.
Lastly, don’t forget to subscribe to get access to all the ready answer for all your
math questions plus other special offers.