Hi guys, have you ever been in a test?
Now in a given question, you look at it you will kind of confuse, and you had a think
why I do this without they have not given us the clues in the question.
Like you look say yeah the question well this minimal mega limited information, how can
I possibly work this out?
Well if you like to know how you to those guys, those top of questions, I am going to
show you this example how we can exercise our resourcefulness, how can it be more resilient
and how to expound to this type of question where the information so limited and this
is the classic example on my left.
– As you can see we have a right angled triangle.
So we have got limited information basically that had not given us any number had they.
And say well we want you to find out what X is up here and we are not going to give
you much information.
When you look around and say we’ve got data here and we have a right angle and it’s
a triangle.
Well what can we do?
Well let us be resourceful, first step in answering this type of question is to write
down what you do have, write that down even if it seems mega limited, write it down.
Let us see what do we have?
Well one of the things we do that we got a thither there that is sound not much but we
have to write it down.
We have thither – yes we have to celebrate we have thither.
Now what else do we have?
We have 90 degrees right there it’s a right angle so we write it down – plus 90 degrees,
okay – now, do we know something about triangle so we could use here for example some sort
of strategy?
One strategy we can use is we know all the angles in a triangle add up to 180 degrees
here so we can use that couldn’t we?
So all these angle – let’s write that up down – if all this angles are equals
into 180 degrees, that means thither right here – 90 degrees right angle right here
plus the missing pro numeral X right over here we could add those three together and
we can get 180 degrees – let’s do that – plus X.
Okay, thither plus 90 plus X is 180.
Thither plus 90 plus X 180 – that seems very plausible and very practical.
Now let’s get X by itself cause we ask to do we are looking to his missing pro numeral
let us get that by itself so let get rid of this guys over here.
How about we take away the 90 degrees from both sides?
So we take way 90 from here, take away 90 from there – which leads us just in thither
over here – thither plus X from up here and that’s going to equal – 90, 90 cancel
here, cancel, cancel, 180 take away 90 leads us to the grand total of 90.
Okay, now let’s bring the X over here – and take away thither from both sides – so take
away thither, take away thither.
Alright, X is the subject now, let’s see what happens – X equals – what do we have
here?
Well 90 minus thither – we do not have a number it is just thither so we write down
thither – 90 minus thither.
Wow!
That’s pretty cool when you look at it because you may or may not have seen this – that
pro numeral right up here is always 90 minus that so no matter what angle you get in here
you just subtract 90 from it and you will get that angle up there.
For example, let’s say the angle down here was 30 degrees here – let’s make a number
up 30 degrees.
And they say, “Find X up there, what’s X?”
Now you know it’s 30, well we know that angles of a triangle is 180, and now we have
this formula, what we will do to find what is X is, is simply use this formula.
X up there for this example – equals, X equals 90 – minus 30 which is thither see
that?
Take away the 30 – therefore X would equal in this situation 30 degrees right up there
X would equal for this example – 90 minus 30 is 60 degrees let’s write that in.
okay, so therefore, we can work out in a right angle triangles knowing that it is 180 degrees,
angle sum of triangle and give us a limited information, just a 30 degrees or something,
we can work out the other angle quite easy.
So look out for this 90 minus thither because it will coming up a bit in this section.
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