<span> 10 < a < 16
1/2 * 10 </span>< 1/2 * а <span>< 1/2 * 16
5 </span>< 1/2 * а < 8
(х-5)(х+5)/(х-5)(х+2)=х+5/х+2
(2-sin(4*a)*ctg(2*a))/sin(4*a)=tg(2*a)
1/(sin(2a)*cos(2a))-cos(2a)/sin(2a) =(1-cos^2(2a))/(sin(2a)*cos(2a))=
<span>=sin^2(2a)/(sin(2a)*cos(2a))=tg(2*a)</span>
=b⁸ : b⁻¹¹ = b⁸⁻⁽⁻¹¹⁾=b⁸⁺¹¹=b¹⁹