<span>Теорема косинусов a2 = b2 + c2 − 2bccosα. </span><span>7^2=3^2+8^2-2*3*8cosα. </span><span>49=9+64-48cosα </span><span>49=73-48cosα </span><span>49-73=-48cosα </span><span>-48cosα=-24 </span><span>cosα=0,5 </span><span>α=60° </span><span>ответ:α=60°</span>
Ответ:
-cos120°
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