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In prisma patrulatera cu l=6cm si h=8cm, aflati:
cos(A'C, (ABD))


Răspuns :

cos(A'C, (ABD)) = cos∡A'CA

AC = AB√2 = 6√2 cm (formula diagonalei in patrat L√2)

A'C = √AC²+AA'² (Pitagora)

= √(6√2)²+8²

= √72+64

= √136

= 2√34 cm

cos∡A'CA = AC/A'C = 6√2/2√34 = 3√68/34 = 6√17/34 = 3√17/17