Dimensions Pythagoras Problem Solving Question

areapythagorean triples

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I have no idea how to work for (b) (c). Help please? Step by Step solution?

Best Answer

Since the books are $20$ mm thick and the gap is $16$ mm, the cosine of the gap angle is $\frac{16}{20}=0.8$. This means the sine is $\sqrt{1-0.8^2}=\sqrt{.36}=.6$ and the height of the gap is $20\times0.6=12$.

Here, corrections were made when the question's author noted that 4 triangles at the base of the books were different from the one in the lower left corner. (See comments below)

The bottom of the box is $x+16+(4\times25)=x+116$, the height of the box is $y+12$, and $x+116=y+12$ so $y=x+104$.

The angles on the right side of box are the complimentary to those on the left so cosine is related to height and sine is related to the base. The length of the books $(z)=\frac{1}{sin}x=\frac{1}{cos}y\quad\text{or}\quad \frac{5}{3}x=\frac{5}{4}y=\frac{5}{4}(x+104)$. Using the least common multiple, we get:

$$\frac{20}{12}x=\frac{15}{12}(x+104)\implies 5x=15\times104\implies x=3\times104 =312$$ The height of the book is a hypotenuse: $z=\frac{1}{sin}x=\frac{5}{3}x=\frac{5}{3}\times 312=520$

The width of a book equals the side of the box: $x+104=312+104=416$.

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