Answer: 
Step-by-step explanation:
Given
For figure (i) both triangles are congruent


For figure (ii)
Two triangles WXZ and WZY are congruent

I think the answer is 43.2 degrees
Split up the integration interval into 4 subintervals:
![\left[0,\dfrac\pi8\right],\left[\dfrac\pi8,\dfrac\pi4\right],\left[\dfrac\pi4,\dfrac{3\pi}8\right],\left[\dfrac{3\pi}8,\dfrac\pi2\right]](https://tex.z-dn.net/?f=%5Cleft%5B0%2C%5Cdfrac%5Cpi8%5Cright%5D%2C%5Cleft%5B%5Cdfrac%5Cpi8%2C%5Cdfrac%5Cpi4%5Cright%5D%2C%5Cleft%5B%5Cdfrac%5Cpi4%2C%5Cdfrac%7B3%5Cpi%7D8%5Cright%5D%2C%5Cleft%5B%5Cdfrac%7B3%5Cpi%7D8%2C%5Cdfrac%5Cpi2%5Cright%5D)
The left and right endpoints of the
-th subinterval, respectively, are


for
, and the respective midpoints are

We approximate the (signed) area under the curve over each subinterval by

so that

We approximate the area for each subinterval by

so that

We first interpolate the integrand over each subinterval by a quadratic polynomial
, where

so that

It so happens that the integral of
reduces nicely to the form you're probably more familiar with,

Then the integral is approximately

Compare these to the actual value of the integral, 3. I've included plots of the approximations below.
2x + y = 10
5x - y = 18
7x = 28
x = 4
2(4) + y = 10
8 + y = 10
y = 2
(4,2)
The answer depends on knowing that 0.4444.... is equal to 4/9;
<span>the square root of 4/9 is 2/3 = 0.6666....</span>