cosA=AC/AB
<span>0,8=AC/8</span>
AC= пощитай
<span>BC*BC= (AB*AB) - (AC*AC)= пощитай</span>
<span>и выведешь BC</span>
<span>(√3+5√7)²=3+10√21+175=178+10√21</span>
= [(tg7π/24 - tgπ/24)(tg7π/24 + tgπ/24)] / [(1-tg7π/24*tgπ/24)(1+tg7π/24*tgπ/24)] = [(tg7π/24 - tgπ/24)/(1+tg7π/24*tgπ/24)] * [(tg7π/24 + tgπ/24) / (1-tg7π/24*tgπ/24)] = tg(7π/24 - π/24) * tg(7π/24 + π/24) = tgπ/4 * tgπ/3 = 1 * √3 = √3
15 мин = 1/4 часа
Х ( км/час ) скорость из села до места
36 / Х = ( 36 / ( Х + 2 )) + 1/4
36 / Х = ( 36•4 + Х + 2 ) / ( 4( Х + 2 )
36 / Х = ( 146 + Х ) / ( 4х + 8 )
36( 4х + 8 ) = х( 146 + Х )
144х + 288 = 146х + х^2
Х^2 + 2х - 288 = 0
D = 4 + 1152 = 1156 = 34^2
X1 = ( - 2 + 34 ) : 2 = 16 ( км/час )
Х2 = ( - 2 - 34 ) : 2 = - 18 ( < 0 )
Ответ 16 км/час
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