Trick for doing trigonometry mentally! - By tecmath
Transcript
| 00:0-1 | You're welcome to take mouth channel . What we're going | |
| 00:02 | to be having a look at in this video is | |
| 00:03 | a good little trigonometry trick and it's used to memorize | |
| 00:07 | the sign and co sign of your basic angles . | |
| 00:10 | These angles zero degrees , 30 degrees , 45 degrees | |
| 00:13 | , 60 degrees and 90 degrees . And these are | |
| 00:17 | the fairly common angles to do this . We're gonna | |
| 00:19 | be using a pretty common instrument . You carry around | |
| 00:22 | with yourself . You're gonna be using your hand . | |
| 00:24 | Okay , So I'll show you how to do this | |
| 00:26 | . Okay , so first off , I'll draw a | |
| 00:28 | picture of a hand here . Okay , hopefully I | |
| 00:30 | can do a nice picture of a hand . Um | |
| 00:32 | I must say I'm not the greatest artist ever . | |
| 00:35 | Okay , there you go . There's my picture of | |
| 00:38 | ahead . It's not too bad . Right ? And | |
| 00:41 | going Left from right here . Okay , I'm going | |
| 00:44 | to label those angles . I was talking about that | |
| 00:46 | 0°. . Okay . We had 30° , 45°, 60° | |
| 00:55 | and then 90°. . Okay . Ah I'm also going | |
| 01:01 | to label the fingers here . Okay . Going outwards | |
| 01:04 | , I've got one two 34 five . So the | |
| 01:10 | first finger there , I've got drawn down as my | |
| 01:13 | thumb typing and it's zero°. . Okay , so again | |
| 01:16 | , going in ascending order from the right to the | |
| 01:20 | left there . So this is the way we can | |
| 01:23 | work out the sign and co sign of this particular | |
| 01:27 | these particular angles . Okay , fairly easy . And | |
| 01:30 | it has follows to say we want to know the | |
| 01:32 | sign of , say 60°. . Actually going to work | |
| 01:35 | out both the sign and the co sign . Okay | |
| 01:37 | , so I'll put down the sign and the coast | |
| 01:41 | side of 60° because let's face it , these are | |
| 01:45 | fairly easy to work out . Yeah , 60°. . | |
| 01:49 | Are you going to see that we have the security | |
| 01:52 | just here . So pretty much the sign values are | |
| 01:56 | the ones which are going to be carrying on the | |
| 01:57 | right here . And the co sign values and the | |
| 02:00 | ones need to be carried on the left here . | |
| 02:01 | And we're just going to do a couple of things | |
| 02:03 | with them , which is as follows . We're going | |
| 02:05 | to get the value we see and we're going to | |
| 02:07 | Square root it and put it over to so I'll | |
| 02:09 | show you what I mean to say . Co sign | |
| 02:11 | of 60 . That's the sign of 60 . It's | |
| 02:14 | this 1 , 2 , 3 fingers here . OK | |
| 02:17 | uh That side there's three fingers . So I get | |
| 02:21 | three fingers , I'm gonna square in them and I | |
| 02:25 | put them over to uh that's our answer . Okay | |
| 02:29 | . The CO sign that's on the left hand side | |
| 02:32 | here . There's one finger there . Okay , I'm | |
| 02:35 | going to square . It is and square to one | |
| 02:37 | is one , and I'll put it over to that's | |
| 02:41 | all there is to it . Right , okay . | |
| 02:44 | Not bad . Right . That's a fairly simple trick | |
| 02:48 | . What about we go through another one of these | |
| 02:51 | ? So what about we do ? Uh I want | |
| 02:52 | to know what the side and co side of say | |
| 03:00 | let's do zero degrees . Okay . So you're going | |
| 03:06 | to see here that we have ? Okay , I'll | |
| 03:10 | put the 10° in here . Okay . And all | |
| 03:14 | the ones on this side are going to be a | |
| 03:15 | co sign of the ones on this side are gonna | |
| 03:17 | be a sign . So pretty easy . Right , | |
| 03:19 | so sign first you see here there's no figures . | |
| 03:22 | Okay , So nothing . All right . That's over | |
| 03:27 | two square it or nothing . So it's we're gonna | |
| 03:31 | we're gonna nothing answer there . What we have here | |
| 03:34 | is we have four fingers for our co sign The | |
| 03:38 | square root of those , which is equal to two | |
| 03:40 | . And we're putting that over to It's it's equal | |
| 03:43 | to one . Okay . I told you this was | |
| 03:48 | going to be a nice simple trick and it is | |
| 03:49 | a fairly simple trick , carry this , calculate around | |
| 03:51 | with you all the time . Okay . What about | |
| 03:55 | one last one of these saying we wanted to work | |
| 03:58 | out the side and cause Of the sign and co | |
| 04:04 | sign of 45°. . Okay . Or on the old | |
| 04:09 | middle digit there . Okay . So What we have | |
| 04:12 | is as follows a sign we got two figures here | |
| 04:15 | . Okay . 1 2 Square It . R two | |
| 04:19 | over to the coast side is a swear at it | |
| 04:22 | too . Over to pretty cool . Right ? So | |
| 04:28 | that's how you do these . Um It's fairly simple | |
| 04:30 | . Just one thing I haven't really mentioned by the | |
| 04:31 | way , but just say you decide at the same | |
| 04:34 | time you're going to work at the tan the tangent | |
| 04:36 | ? Well that's fairly simple to , because all you | |
| 04:38 | really need to do is you need to just remember | |
| 04:40 | that the tan is equal to sign over , cause | |
| 04:45 | so as long as you know your sign and you | |
| 04:47 | know , your cause you can put one over the | |
| 04:48 | other , you've got the town as well . Pretty | |
| 04:51 | cool . Right ? So that's a great little way | |
| 04:53 | of doing this . It's fairly simple . Um Anyway | |
| 04:56 | , hopefully you find this a handy little trick . | |
| 04:58 | Okay , see you next time . Bye . |
Summarizer
DESCRIPTION:
OVERVIEW:
Trick for doing trigonometry mentally! is a free educational video by tecmath.
This page not only allows students and teachers view Trick for doing trigonometry mentally! videos but also find engaging Sample Questions, Apps, Pins, Worksheets, Books related to the following topics.
GRADES:
STANDARDS:
