What to know for trigonometry?

Answer 1

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 theta

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 problem)

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 side

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.