Basic Trigonometry - Fast Math Lesson! - Free Educational videos for Students in K-12

Basic Trigonometry - Fast Math Lesson! - By tecmath

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00:03	before I started what trigonometry is . I just want
00:05	to do a quick refresher , a few things about
00:07	triangles . Yeah . The trial was , we're going
00:10	to be dealing with right angle triangles and they look
00:13	like this . Okay . They have three sides of
00:17	triangles do and they have A 90° angle which is
00:23	just down here , the same angle that you get
00:25	squares and rectangles . The other little thing which I
00:29	mentioned before we get on trigonometry , All the angles
00:32	in a triangle at up to 180°. . Okay ,
00:37	so now we're all ready to go in trigonometry trigonometry
00:42	, there's a process that shows the relationship between the
00:44	sides and the angles in a right angle . Trying
00:47	, okay , if we know what a couple of
00:49	the sides are , one of the angles is we
00:50	can work out what any other one of the sides
00:52	or angles are using trigonometry . So I'll get on
00:55	to how that works right now . Well we have
00:57	to do first is you have to put a few
00:59	labels on this right angle trying to describe the different
01:01	angles in the different sides . 1st 1 I'm going
01:04	to do is I'm going to put the one on
01:06	to describe an angle here is called feta it's an
01:09	unknown angle or maybe it is a known angle .
01:11	We can use it to work outside . Okay .
01:13	The other thing you have to know is how what
01:15	the sides are called side here , directly opposite feeder
01:19	is called the opposite . The longest side is called
01:23	the high pot news . The other side is called
01:27	the adjacent Yeah , that's the labels out of the
01:30	way . True economic functions that we're going to be
01:33	using you've probably heard of in school aside because two
01:41	, as far as you guys need to really know
01:43	, these are buttons that you're going to press on
01:44	a calculator . Yes . Sign . Because in town
01:48	to work at which sides and angles they deal with
01:51	. What we'll do is I'll show you this little
01:53	new mind when you go to school . You probably
01:56	got given this one soccer tower and you might have
01:58	told some weird little story about indians and things like
02:02	that which Have one maths teacher say . But another
02:05	math teacher , I worked it out . Remember this
02:08	without trying to do something because I can never quite
02:10	spell it . At least have a really nasty math
02:12	teacher . Really old angry math teacher . We remembered
02:16	soccer tower . This one caused hand thing like this
02:21	. Some old hags can't always hack their old age
02:25	. Now the way we use this is the first
02:27	, we'll consider signing the some old hags part .
02:30	So sign signed feeder . We're dealing with the angle
02:34	equals the opposite over the high part . Use Okay
02:42	, casa , cause freedom is the adjacent over the
02:50	news tan feeder here is the opposite over the adjacent
03:01	. All right . I'll show you how this works
03:02	. Okay , So the first example we look out
03:04	here Is an example where we have an angle of
03:06	25° The height of the triangle of seven . We
03:10	want to know an unknown length here , which is
03:12	shown as X . Okay . So I've written the
03:16	steps down here about how I do this . The
03:19	first thing to do , I would label the sides
03:22	the opposite the adjacent and the hype his seven here
03:26	is opposite the angle . So it's alongside here is
03:30	the hypothesis . We might be using that for the
03:32	other side is the adjacent . Have done that .
03:37	The next thing I do is determine which to economic
03:39	function to use sign cosmo Tan . So I go
03:43	tomorrow sine equals opposite over this part over here .
03:47	And what I do with that is able to the
03:49	function that uses opposite and adjacent . Which is it's
03:54	all right over here Tan sweeter because the opposite over
04:00	the adjacent . The next thing I'll do is substituting
04:05	the value 10 ft to become his 25 . That's
04:10	the angle 25°. . It was the opposite which is
04:14	seven over the adjacent which is the side we're actually
04:18	trying to find . I've done that . You calculate
04:22	this first off , I'm going to have to get
04:24	this X . Here by itself the unknown side .
04:27	So alright , X equals Now this step now Tends
04:32	to confuse a few people . They never know quite
04:34	whether to divide or times or things like this .
04:36	Little trick I do for this is I have a
04:38	thing which I write down three equals six , divided
04:42	by two . Okay . Yeah . As you probably
04:46	might notice three or 62 is very similar looking at
04:50	a sum to 10 25 equals seven over X .
04:52	Okay . Something equals something over something else . So
04:55	who was the line these up ? The X .
04:57	Is in the same position as the . Okay ,
05:01	these guys are both in the same position . Yeah
05:06	. What would I do ? Six and three to
05:08	get to ? Well I just six divided by three
05:10	would be this one here divided by this one here
05:13	. So I'm going to do the same . This
05:14	one here which is seven provided by This one here
05:20	which is 1025 . 10 24 . Yes . And
05:27	then I can work this out . First off we'll
05:28	work at what ? Tan 25°. . So to do
05:31	this 25 My 1st 10 on calculator . Get the
05:36	answer . Zero 0.47 So my answer is going to
05:42	be seven divided by .47 seven divided by .47 .
05:49	Give me an answer . The 14.9 . So the
05:56	unknown side Lee is 14.9 . That's up to tom
06:02	. We got one more example . Okay in this
06:06	example here we have an angle of 34°. . We
06:09	have a side length height of three . We have
06:12	an unknown big long diagonal here . So the first
06:15	thing I do his label sides . Okay . Inside
06:19	opposite . The angle here is the opposite to be
06:21	alongside . Here's the high point . So I've labeled
06:24	the two sides were dealing . The next thing I
06:27	do is determine which to economic function we're using .
06:30	Okay . The one that uses the opposite and the
06:31	high cotton . You saw him to sign feeder .
06:37	It was the opposite over the high partners . Now
06:41	I substituting values so sign . So you know the
06:45	angle we're dealing with 34°. . It was the opposite
06:50	which is three over the high part news which is
06:54	the unknown side . Yeah . Alright . Mine .
06:58	three people . 6/2 again they look once again .
07:03	So Yeah . To the same spot sometime To get
07:08	to I'd go six divided by three . Mhm .
07:11	This six is in the same spot as a 33
07:14	divided by signed 34 is and three in the same
07:19	spot so so 34 people is Okay I'll work out
07:27	what signed 34 years 34 sign is .56 three divided
07:37	by 0.56 . I expect an answer around about five
07:42	point something we'll have a look three divided by 0.56
07:49	Vehicles . five point through six . I'll have a
07:56	look at a different example now one where I know
07:59	both the sides and how I might work at the
08:01	angle . Okay . in this example here , as
08:06	you'll see , I don't know the angle but I
08:08	know both the sides . So the first thing the
08:10	steps exactly the same . First thing I do is
08:12	label the sides and dealing with the opposite . Not
08:16	quite news up here , but I'm dealing with the
08:18	adjacent . So the one that deals with the opposite
08:20	adjacent is 10 ft 10 ft up equals opposite over
08:26	the adjacent . Look . I've just done that step
08:29	that step and now I'm about to do this step
08:31	will substitute that . I use turn feeder equals the
08:34	opposite , Which is 1.5 Over 1.3 equals the way
08:42	the workers have . So I get my calculator 1.5
08:49	divided by one 0.3 eagles . I'll get this answer
08:54	at $1.15 right down here . 1.1 slide . Now
08:58	with this button , I press just inverse and they're
09:03	not hit the standby . Okay . Some calculators that
09:06	might be also a second function or something like that
09:09	or it might come up . It's a button that
09:11	comes up like this Tan -1 . It's universal .
09:15	So it's doing it backwards step . So good universe
09:20	time And my angle is 49° 49 degrees . Pretty
09:30	easy . So if you're able to label all the
09:33	sides of a triangle , if you're able to actually
09:36	uses some old house , can't always have their old
09:38	age and apply this properly . You could do really
09:41	well using trigonometry . Next video , we're going to
09:43	work out all the sides and angles of a triangle
09:46	. Okay .

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