, find (in degrees). Round off your answer to the nearest integer.
In the above diagram,
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Let B A = A E = E D = D C = 1 . Since △ E D C is isosceles, ∠ D E C = E C D = 4 0 . Also, △ E A B is isosceles so ∠ A B E = B E A = 2 5 . Now ∠ B E C = 1 2 0 − 2 5 − 4 0 = 5 5 .
By law of cosines on △ E D C , we have
w 2 = 1 2 + 1 2 − 2 ( 1 ) ( 1 ) ( cos 1 0 0 ) ⟹ w = 1 . 5 3 2 1
By law of cosines in △ E A B , we have
y 2 = 1 2 + 1 2 − 2 ( 1 ) ( 1 ) ( cos 1 3 0 ) ⟹ y = 1 . 8 1 2 6
By law of cosines in △ B E C , we have
z 2 = 1 . 8 1 2 6 2 + 1 . 5 3 2 1 2 − 2 ( 1 . 8 1 2 6 ) ( 1 . 5 3 2 1 ) ( cos 5 5 ) ⟹ z = 1 . 5 6 4 3 2
By law of sines in △ B E C , we have
1 . 8 4 2 6 sin θ = 1 . 5 6 4 3 sin 5 5
θ = 7 1 . 6 5
Finally, x = ∠ E C D + θ = 4 0 + 7 1 . 6 5 = 1 1 1 . 6 5 ≈ 1 1 2