You can put this solution on YOUR website! solve the equation for x.
arctan x = arccos(5/13)
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arccos(5/13) means an angle whose cos=5/13=adjacent side/hypotenuse
opposite side=√(13^2-5^2)=√(169-25)=√144=12 (by Pythagorean Theorem)
tan=opposite side/adjacent side=12/5
arctan x=the same angle whose cos=5/13
arctan(12/5) = arccos(5/13)
x=12/5
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