What to know for trigonometry?

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2011-08-08 11:49:56

The absolute basics to trigonometry.

You will need a calculator for this, unless you want to

do it the old and amazingly accurate (for it's time) trig tables

that used to be used (if you can find one)

First you have to understand that basic trigonometry does not

cover any more than right angled triangles

Secondly, the names of the sides of a triangle. The side

opposite to the right angle is known as the hypotenuse (will

abbreviate to hyp). The side opposite to the angle that you wish to

find or the known angle (DO NOT USE THE RIGHT ANGLE AS AN ANGLE) is

known as the opposite side (opp). The other side is known as the

adjacent (adj) (if your triangle has more than three sides there is

a problem).

generally the angle that you wish to find will be known as


the basic rules to trigonometry can be summarized in one easy to

remember word

SOHCAHTOA more easily understood as SOH|CAH|TOA

(the equation that you use is dependent on the the sides

available and what information is given a the beginning of the


SOH means that Sine(theta) = Opp/Hyp

CAH means that Cos(theta) = Adj/Hyp

TOA means that Tan(theta) = Opp/Adj

The angle theta can also be calculated by using the formulas

Theta = sin-1(opp/hyp)

Theta = cos-1(adj/hyp)

Theta = tan-1(opp/adj)

where the -1 means that the trigonometric function simply is

applied to the whole other side of the equation and does not affect

the side that was not originally on

Note: anything in brackets after a sin, cos or tan is part of

that sin, cos or tan. It cannot be separated unless you apply the

inverse (-1 ) to the other side and remove it from it's original


Another note: Sin is pronounced Sine (like swine without the

'w') all the maths teachers that I know hate it when it is

pronounced Sin.

Finally: Trig is not that hard, all that hard work was done when

it was made (and even when past generation had to trawl through

tables to find the right (approximate to maybe three decimals)

number. All that you really need is to know basic algebra, how to

use a scientific calculator, and SOHCAHTOA.

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