Find all symbolic solutions of the equation cos2x 517 in th

Find all symbolic solutions of the equation

cos^2(x) = 5/17 in the interval [0, ].

If there is more than one answer, enter them in a list separated by commas. Decimal approximations will be marked incorrect. Symbolic expressions such as arctan(5) are accepted.

(Please note: this is the third time I am posting this question. The last two answers received were wrong because the directions were not followed correctly. Answers marked wrong: 1/2 cos^-1(-7/17) and cos^-1(sqrt of 5/17)

Solution

cos^2x = 5/17

cosx = +/- sqrt(5/17)

x = cos^-1(sqrt(5/17) )

x = pi - cos^-1(sqrt(5/17) )   { cos is -ve in IIn quad and IIIrd quad)

but x = pi+ cos^-1(sqrt(5/17) )   It is out of given range of [ 0, pi]

So, Solution : ( arccos(sqrt(5/17) ) , pi - arccos(sqrt(5/17) ) )