Răspuns:
Pt α= 0°
R=a+b=3+4=7
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α=60°
R²=a²+b²+2abcosα
R²=3²+4²+2*3*4*cos60
=9+16+24/2
=25+12=37
R=√37
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α=90
R²=a²+b²
R²=3²+4²=9+16=25
R=√25=5
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α=180°
R=a-b=3-4= -1
Explicație: