Find the area of the trapezoidal cross-section of the irrigation canal shown below. Your answer will be in terms of h, w, and θ.

[w + (h/tan θ)] × h
We aim is to find the area of the trapezoidal cross-section of the irrigation canal.
The formula for the area of the trapezoid is [tex]\boxed{\boxed{ \ Area = \frac{1}{2} \times (a + b) \times h \ }}[/tex]
We assume the lower side is [tex]\boxed{ \ a = w \ }[/tex] and the upper side is b = x + w + x or [tex]\boxed{ \ b = w + 2x \ }[/tex]. See the attached picture.
In the right triangles located on the left and right of the trapezoid, we calculate the value of x based on trigonometric ratios namely tan of theta.
[tex]\boxed{ \ tan \ \theta = \frac{opposite}{adjacent} \ }[/tex]
[tex]\boxed{ \ tan \ \theta = \frac{h}{x} \ }[/tex]
[tex]\boxed{ \ x = \frac{h}{tan \ \theta} \ }[/tex]
Substitute the equation of x to [tex]\boxed{ \ b = w + 2x \ }. [/tex]
We get [tex]\boxed{ \ b = w + \frac{2h}{tan \ \theta} \ }[/tex]
Finally all components are complete and can be substituted into a formula to calculate the area of a trapezoid.
[tex]\circ \ \boxed{a = w}\\ \circ \ \boxed{ \ b = w + \frac{2h}{tan \ \theta} \ }\\\circ \ and \ h[/tex]
[tex]\boxed{ \ Area = \frac{1}{2} \times (w + w + \frac{2h}{tan \ \theta}) \times h \ }[/tex]
[tex]\boxed{ \ Area = \frac{1}{2} \times (2w + \frac{2h}{tan \ \theta}) \times h \ }[/tex]
[tex]\boxed{ \ Area = \frac{1}{2} \times 2(w + \frac{h}{tan \ \theta}) \times h \ }[/tex]
Hence, the area of the trapezoidal cross-section of the irrigation canal is [tex]\boxed{\boxed{ \ Area = (w + \frac{h}{tan \ \theta}) \times h \ }}[/tex]
Keywords: the trapezoidal, cross-section of the irrigation canal, the area, the answer will be in terms of h, w, and θ, trigonometric ratios, tan, opposite, adjacent, height, sides
The area of the trapezium is [tex]\boxed{\left({w+\frac{h}{{\tan \theta }}}\right)h}[/tex] .
Further explanation:
The area is the trapezium can be calculated as,
[tex]{\text{area of trapaezium}}=\frac{1}{2}\times\left({{\text{sum of parallel sides}}}\right)\times{\text{height}}[/tex]
The trigonometry ratio used in the right angle triangles.
The tangent ratio can be written as,
[tex]\tan \theta = \frac{{{\text{length of the side opposite to }}\theta }}{{{\text{length of the side adjacent to }} \theta }}[/tex]
Here, base is the length of the side adjacent to angle [tex]\theta[/tex] and the length of side opposite to angle [tex]\theta[/tex] is perpendicular.
Step by step explanation:
Step 1:
Do naming the given trapezium as attached in the figure.
After naming we have [tex]PQRS[/tex] is a trapezium
Consider [tex]h[/tex] as the height of the trapezium in which [tex]{\text{X and W}}[/tex] are the points drawn on the line segment [tex]RS[/tex] .
The measurement of one of the parallel side [tex]PQ[/tex] is [tex]w[/tex]
It can be seen from the attached figure that [tex]RQ{\text{ and }}SP[/tex] are the transversal lines.
Therefore, by alternate interior angle property [tex]\angle QRW=\theta{\text{ and }}\angle PSX=\theta[/tex] .
The another parallel side can be written as [tex]SR=SX+XW+WR[/tex] .
Consider the sides as [tex]XW=w,SX=x,WR=x[/tex] .
Therefore, the parallel side can be written as [tex]SR=x+w+x[/tex] .
Step 2:
Now in the right angle triangle [tex]XSP[/tex] the tangent ratio can be applied as,
[tex]\begin{aligned}\tan \theta &=\frac{{{\text{length of the side opposite to }}\theta }}{{{\text{length of the side adjacent to}}\ \theta }}\hfill\\\tan \theta &=\frac{h}{x}\hfill\\x&=\frac{h}{{\tan \theta }}\hfill\\\end{aligned}[/tex]
Now substitute the value of [tex]x[/tex] in the equation [tex]SR=x+w+x[/tex] .
[tex]\begin{gathered}SR=\frac{h}{{\tan \theta }}+w+\frac{h}{{\tan \theta }}\hfill\\SR=2\frac{h}{{\tan \theta }}+w\hfill\\\end{gathered}[/tex]
Step 3:
The area of the trapezium can be calculated as,
[tex]\begin{aligned}{\text{area of trapaezium}}&=\frac{1}{2}\times\left({{\text{sum of parallel sides}}}\right)\times{\text{height}}\\&=\frac{1}{2}\times\left({PQ+SR}\right)\times h\\&=\frac{1}{2}\times\left({w+w+\frac{{2h}}{{\tan \theta}}}\right)\times h\\&=\frac{1}{2}\times\left({2w+\frac{{2h}}{{\tan \theta }}}\right)\times h\\\end{aligned}[/tex]
Further simplify the above equation.
[tex]\begin{gathered}{\text{area of trapaezium}}=\frac{1}{2}\times\left({2w+\frac{{2h}}{{\tan\theta}}}\right)\times h\hfill\\{\text{area of trapaezium}}=\left({w+\frac{h}{{\tan \theta }}}\right)h\hfill \\\end{gathered}[/tex]
Therefore, the area of the trapezium is [tex]\left({w+\frac{h}{{\tan\theta }}}\right)h[/tex] .
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Answer details:
Grade: High school
Subject: Mathematics
Chapter: Perimeters and area
Keywords: trapezium, area, parallel sides, sum, height, length, opposite side, adjacent side, trigonometry, tangent ratio, perpendicular, base, hypotenuse, right angle triangle.