∠CEB and ∠AED are vertical angles, which means they must be equal to each other. Make them = x in an equation. The angles form a quadrilateral, so the sum of the interior angles must equal 360°.
77 + 77 + x + x = 360 Combine like terms.
154 + 2x = 360 Subtract 154 from both sides.
2x = 206 Divide both sides by 2.
x = 103
∠CEB is greater than 90°, so it must be an obtuse angle.
The maximum value attained by the function will be 4 4 = 4cos(2x - π) cos(2x - π) = 1 2x - π = 0 x = (nπ)/2 From x = 0 to x = 2π, n = 1, 2, etc The equation will yield +4 for odd values of n and -4 for even values of n
