Q13 of 142 Page 11

If sec x cos 5x + 1 = 0, where find the value of x.


cos 5x = -cos x


cos 5x+cos x = 0


We know



Here



Now from the above equation it would be,


2cos 3x cos 2x=0


cos 3x cos 2x=0


cos 3x=0 or cos 2x=0


for cos3x=0




for cos2x=0




so the values of the x less than equal to 90° are


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