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2014-08-25T04:47:19+03:00
ΔABC, mas<A=90
[AD] _|_ [BC]
[AD]-h

ΔABD, mas<D=90
AD²=AB²+BD²=15²+9²=225+81= 306   =>AD=3√34

ΔABC, mas<A=90
AD²=BD*DC

306=9*DC  =>DC=306/9= 34

BC=BD+DC=9+34= 43

AC²=BC² -AB²= 43² -15² = 1849-225= 1624   =>AC=2√406

ADC, mas<D=90
cos<DAC=AD/AC=  3√34/2√406= 3√13804/2*406=

=3 * 2√3451/2 *406= 3√3451/406
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