основание авсd. ас=ав√2=18√2. тогда ав=18
высота so (о-центр основания, точка пересечения диагоналей), ао=1/2ас=9√2
треугольник asb - равнобедренный ан - высота боковой грани,
угол sно - угол наклона бок.грани к плоскости основания
треугольник sно - прямоугольный. угол о = 90 град. угол н=45 град. тогда угол s = 45 град. значит, треугольник - равнобедренный sо=он, он=1/2аd=1/2*18=9. sн=он√2=9√2
площадь бок. поверхности = 4*s(треугольника аsв)=4*1/2*sн*ав=2*9√2*18=324√2
пересекаются в точке о. найдите отношение площадей треугольников aob и cod.
as the moon rose, they went on their way. As they were moving to the north, they
began to meet the patrols of the French army. The first sentinel saw them and
asked who they were. Heyward told him in French that he was a French officer
and was taking the two daughters of the commander of an English fort to the
French General. Luckily the sentinel believed him and let them pass.
Morning was just beginning. The mountain on which they stood was about a
thousand feet high. The mountains around it were not so high, so the travellers
had a good view of the surroundings. To the north of them lay a large lake. On
the shore of the lake they saw the low buildings and the walls of William Henry.
The land around the Fort had been cleared of wood for some distance. In
different places the travellers could see the sentinels who held a watch against the
enemy. To the south-east of the Fort they saw an entrenched camp in which
Heyward recognized the troops which had left Fort Edward a few minutes before
them. From the woods a little farther to the south rose the smoke of many camp
fires, which showed the presence of Indians. To the south-west, on the shore of
the lake Heyward saw many white tents, guns and a lot of soldiers. There could
be about ten thousand men there, he thought.
So the army of the French General had already arrived at the walls of William
Henry. As the travellers were looking down at the scene which lay like a map at
their feet, they heard the roar of artillery.
“We are a few hours too late,” said the scout. “The French General has already
filled the woods with his Mingoes.”