A^2=(C+Bcosφ)^2+(Bsinφ)^2
=C^2+2BCcosφ+B^2(cos^2φ+sin^2φ)
=C^2+2BCcosφ+B^2
cosφ=(A^2-B^2-C^2)/2BC
=(5.3^2-1-4.5^2)/(2*4.5*1)
=0.76
P=100V×Bcosφ
=100×4.5×0.76
=342[W]
(答):(1)
A^2=(C+Bcosφ)^2+(Bsinφ)^2
=C^2+2BCcosφ+B^2(cos^2φ+sin^2φ)
=C^2+2BCcosφ+B^2
cosφ=(A^2-B^2-C^2)/2BC
=(5.3^2-1-4.5^2)/(2*4.5*1)
=0.76
P=100V×Bcosφ
=100×4.5×0.76
=342[W]
(答):(1)