Processing Math: Done

From Förberedande kurs i matematik 1

An often-used technique to calculate cos v and tan v, given the sine value of an acute angle, is to draw the angle v in a right-angled triangle which has two sides arranged so that sin v=57.

Using Pythagoras' theorem, we can determine the length of the third side in the triangle.

x2+52=72 which gives that x=72−52=24=26 

Then, using the definition of cosine and tangent,

cosv=x7=726tanv=x5=526

NOTE: Note that the right-angled triangle that we use is just a tool and has nothing to do with the triangle that is referred to in the question.