Answer:
Area 5 x 8 = 40cm^2
If 5cm is a perpendicular height then of course its 40cm
But if its slant height then we can do the following by flipping the triangles diagonal to find the longer length that sits perpendicular with the perpendicular line.
47.2cm^2 if using full decimal in diagonal finding
and if rounding diagonal fining to 9.4cm we x by 5 we get 9.4 x 5 = 47cm^2
Explanation:
Parallelogram no height
Step 1 we use Pythagoras to get the diagonal measure so we can flip the triangle measure and re calculate .
sqrt of 25+ sqrt 64 = sq rt 89 = 9.43
9.43cm is your hypotenuse diagonal
and then deduct 9.43 - 8 = 1.43cm x 5 use that length and area to deduct from 8x 5 = 40
1/2 x 9.43 x 5 = 23.575
1/2 x 1.43 x 5 = 3.575
23.575 - 3.575 = 20
20+20 = 40cm
If this is shown its proven the slant has been added and taken away.
To represent the method if just slant was given and no height.