Sin, Cos and Tan. (1 Viewer)

[Netty_M]

I hate this and it seems like I don't get ANY of it. Am I the only one that doesn't understand this? Because I am feeling really stupid right now... I hate not knowing how to do things, it makes me feel dumb.

 

[FinalFantasy]

yea i hate not knowing how to do things too!
but ya gota deal w\ it....
wat parts of this "Sin, Cos and Tan" are you having problems with?

 

[SaHbEeWaH]

well i'm not sure what sin cos and tan are used for in general, but in general... (no pun-intended) ...

sin is the ratio of the opposite side to the hypotenuse of a right-angled triangle
cos is the ratio of the adjacent to hypotenuse in a RA triangle
tan is the ratio of the opposite to the adjacent in a RA triangle

it's always followed by some sort of variable which corresponds to an angle and becomes its subject

so sin x refers to the ratio of the opposite side of angle x to the hypotenuse

A
|\
|..\
|....\
|......\
|........\
|____y\
B...........C

(ignore the .'s)

in this right angled triangle for example:

sin y would be the ratio of opp to hyp i.e. AB to AC
so we express this as sin y = AB/AC
cos y would be the ratio of adj to hyp i.e. BC to AC, cos y = BC/AC
tan y would be the ratio of opp to adj i.e. AB to BC, tan y = AB/BC


i'm not sure what kinda questions you do in this but here's an example:

..A
..|\
..|..\
..|....\
x|......\2
..|........\
..|___60\
..B...........C

find x

we know that sin @ = opp/hyp
so from the diagram,

sin 60 = x/2
2(sin 60) = x [multiplying both sides by 2]

punch that into your calculator and we get an approximate value of x as 1.732...


..A
..|\
..|..\
..|....\
..|......\5
..|........\
..|____x\
..B...3......C

here's another example where you need to find angle

we know cos @ = adj/hyp

so, cos x = 3/5

then press the [cos^-1] button
it's usually shift cos
then punch in 3/5 with the fraction a^b/_c button not division as this will give a different answer

and you should get 53.1301.....
hit the [^o ' ''] button and it'll give it to you in degrees
53^o7'48.37''

my guess is that general maths doesn't go much further than that?
or am i wrong ...

 

[Dreamerish*~]

remember when it comes to the triangle:

SOHCAHTOA

sin = opposite/hypotenuse
cos = adjacent/hypotenuse
tan = opposite/adjacent

opposite = the side which the angle specified is not touching at all, hence the opposite side
adjacent = the side which the angle specified is touching, but is not the longest side
hypotenuse = the longest side of the triangle

that being said, is there anything specific you don't understand?

 

[Netty_M]

How do I find the value of a pronumeral when there is no right angle??

 

[INXS]

Yeah post the question(s) that you are having trouble with. Take the advice from the above posts, and you can't go wrong!

 

[FinalFantasy]

How do I find the value of a pronumeral when there is no right angle??

u mean there's there's an unknown value on one of the 3 sides of the triangle and it's not a right angle and u want to find that unknown value?

 

[INXS]

Just post the question, and things will be so much easier.

 

[SaHbEeWaH]

use the sine or cosine rule, sub in values and solve
it should be on your formula sheet or something or other

sine rule
a/sinA = b/sinB = c/sinC

cosine rule
c² = a² + b² - 2ab*cosC

remember in this formula, A B C are the angles
a b c are the sides where side a is the side opposite to angle A
b opp to angle B
c opp to angle C

just sub in stuff now basically...

 

[Netty_M]

Thank you all very much for your help, I think I'm starting to get it now. I appreciate all your input very much.