<span>The exact solution of cos (17</span>π<span>/6) is as follows:
First change the angle into degrees.
17(</span>π/6) (180°/π) = 510°
Then we calculate the cosine of the angle above and it as follows:
cos 510° = -(√3)/2
Hope this answers the question. Have a nice day.

∠ Given are (x + 18)° , x° , 4x° and one Angle is 90° as per diagram
Let ,
1st∠ = (x + 18)°
2nd∠ = x°
3rd∠ = 4x°
so ,

substituting x = 12 at the place of x .
= x° + 18°
= 12° + 18 °
1st∠ = 30°
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= x°
2nd∠ = 12°
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= 4x°
= 4(12)°
3rd∠ = 48°
It would be a right scalene triangle.
hope this helped :)