Formulas of cosine, sine and tangentLearn this trick :
By grouping letters 3 by 3 (two on the top and one below), it permits to keep in mind these 3 formulas which are very useful :
For you who knows well the cosine, this part of the site is easy : it is exactly the same thing except that there are two more formulas. Here are two examples to practice.
Using trigonometry formulasCalculate CI.
Since we already know one angle, we have the opposite edge and we are looking for the adjacent edge, so we need the formula of the tangent.
And here comes the other example :
Calculate the angle .
To find the angle we are looking for, we have the opposite edge and the hypothenuse, so it is the formula of the sine that we need.
Be careful with the last but one step which is done with the calculator, teachers do not like you to write on the sheet because the sign (-1) has nothing to do with powers.
See also : trigonometry on fmaths.com