Respuesta :

calculista
see the picture attached to better understand the problem

we know that
in the right triangle ABC

cos 70°=adjacent side angle 70°/hypotenuse
adjacent side angle 70°=AB
hypotenuse=AC-----> 25 mm
so
cos 70°=AB/25-----> AB=25*cos 70°------> AB=8.55 mm

the answer is
the side adjacent a 70 degree angle is 8.55 mm long
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