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# help me with my maths

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how does sinus cosinus and tangens works???

Jun 18, 2020
edited by Guest  Jun 18, 2020
edited by Guest  Jun 18, 2020

#1
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I believe you meant $$\sin(x), \cos(x)\text{, and }\tan(x)$$.

We have a mnemonic for that, namely "SOHCAHTOA".

In the following diagram:

AB is opposite to x, so we call it "opposite side"

BC is the "hypotenuse".

The mnemonic "SOHCAHTOA" helps us remember the following relations:

$$\color{red}\text{s}\color{black}\text{in}\;x = \dfrac{\color{red}\text{o}\color{black}\text{pposite side}}{\color{red}\text{h}\color{black}\text{ypotenuse}}$$

$$\color{red}\text{c}\color{black}\text{os}\;x = \dfrac{\color{red}\text{a}\color{black}\text{djacent side}}{\color{red}\text{h}\color{black}\text{ypotenuse}}$$

$$\color{red}\text{t}\color{black}\text{an}\;x = \dfrac{\color{red}\text{o}\color{black}\text{pposite side}}{\color{red}\text{a}\color{black}\text{djacent side}}$$

Jun 18, 2020
#2
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ohhh sound logical,

but how do i calculate a side like from a triangle ABC i know AB and AC but i want to know BC, for example AB is 5 metres and AC is 9 Metres...

thanks btw!

Guest Jun 18, 2020
#3
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Hello Guest:

Is any angle given? I mean, are there any right angles?

If yes, then you don't need sin, cos, or tan. You can calculate it directly by Pythagorean theorem.

MaxWong  Jun 18, 2020
edited by MaxWong  Jun 18, 2020