2.6.2.30 Trigonometric Fourier Series

Condition: coefficient \ (a_ {15} \) decomposition in a row Fourier on the segment \ ([-4; 4] \) functions \ (f (x) =-5 x^{2} +5 \) is calculated by the formula? 1) \ (\ frac {1} {4} \ int _ {-4}^{4} \ left (-5 x^{2} +5 \ right) \ sin \ left (\ frac {15 \ pi x} \ right) d x \) 2) \ (( a_ {15} = 0 \) 3) \ (\ frac {1} {4} \ int _ {-4}^{4} \ left (-5 x^{2} +5 \ right) \ cos \ left (\ frac {15 \ pi x} {4} \ right) d x \) 4) \ \ (\ frac {2} {4} \ int_ {0} {4} \ left (-5 x^{2} +5 \ right) \ cos \ left (\ frac {15 \ pi x} {4} \ right) d x \) 5) \ (\ frac {2} {4} \ int_ {0} {4} \ left (-5 x^{2} +5 \ right) \ sin \ left (\ frac {15 \ pi x} {4} \ right) d x \)