Hypothesis: volumes of both figures are equal.the volume of figure 1 is:
![v_1=a_{basis}\cdot h=\frac{1}{2} \cdot 5\cdot7\sin \alpha\cdot 8=280\sin \alpha](/tex.php?f=v_1=a_{basis}\cdot h=\frac{1}{2} \cdot 5\cdot7\sin \alpha\cdot 8=280\sin \alpha)
.the volume of figure 2 is:
![v_2=a\cdotb\cdotc=5\cdot7\cdot8=280](/tex.php?f=v_2=a\cdotb\cdotc=5\cdot7\cdot8=280)
.since
![0\le \alpha\le \pi](/tex.php?f=0\le \alpha\le \pi)
, you can conclude that
![0\le\sin\alpha\le1](/tex.php?f=0\le\sin\alpha\le1)
and
![0\le v_1\le 140](/tex.php?f=0\le v_1\le 140)
. so,
![v_1\le v_2](/tex.php?f=v_1\le v_2)
.volumes of figures are equal only when an angle in the basis is right (then figures will be the same), in another cases volume of figure 1 is less than volume of figure 2.the hypothesis was not correct in all cases.