Cos(x)=1/4

Question

The original problem was 4cos2x−9cosx+2=0 They want to know the smallest positive number that x can be. I solved part of it using the quadratic formula getting Cos(x)= 1/4, 2. I don't know how to solve for x.

Answer 1

You did well by solving the quadratic, and you seem to have spotted that cos(x) can't be 2 because the cosine function can't give a result greater than 1 or less than -1. x=arccos(1/4) or x=cos^-1(1/4) is how the answer is found. This may be a function on your calculator. If you use tables you would look in the body of a cosine table to find what angle gives you a cosine of 0.25. The answer is 75.52 degrees approximately.

Answer 2

get the invers kosine(0.25)...75.52248781527969 deg

need a bigger kalkulater that du trig funks