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Observe that B F E D , A F G E , B C D E are all cyclic quadrilaterals.
In B F E D , we have ∠ F D E = ∠ F B E = 4 1 0 .
Also, in B C D E , we have ∠ D C E = 3 2 0 = ∠ D B E .
Now observe that in △ A B D D F and B E are altitudes intersecting at G .
Hence, G is the orthocenter of △ A B D which implies ∠ A G D = 1 8 0 0 − ∠ A B D = 1 8 0 0 − ( 4 1 0 + 3 2 0 ) = 1 0 7 0 .
As F G D is a straight line, we have ∠ A G D + ∠ A G F = 1 8 0 0 ⇒ ∠ F G A = 7 3 0 .
Applying angle sum rule in triangle F A G , we get ∠ G A F = 1 7 0 .
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Join FE, and FC . Since BCDE, is a rectangle, so BCDE is a circle. In quadrilateral BCDF sum of opposite angles ∠ D F B + ∠ B C D = 1 8 0 . ∴ i t i s c y c l i c . ⟹ B C D E F i s a c i r c l e . ∠ C E B = ∠ D E B − ∠ D E C = 3 2 . A n g l e s o n c h o r d F C , ∠ C D F = ∠ C E F , ⟹ ∠ C D E − ∠ F D E = ∠ C E B + ∠ B E F ⟹ 9 0 − 4 1 = 3 2 + ∠ B E F . ∴ ∠ B E F = 1 7 . I n q u a d r i l a t e r a l A F G E , ∠ s a t F , a n d E a r e 9 0 o , ∴ i t i s c y c l i c . ∴ ∠ G A B = ∠ B E F = 1 7