I decide: the length and diagonal are given. Find the width of the rectangle.
Given: a=10.5 cm; c=18.2 cm; α=90°(rectangle); b-?
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By T. Pythagoras
c²=a² + b²
b²=c²-a²
b=√(c²-a²)=√(c-a)(c+a)=
√(18.2 - 10.5)(18.2 + 10.5)=
√(7.7 * 28.7)=√(7*1.1 * 7*4.1)=7√4.51≈14.8657≈14.87 cm is the answer.
14cm 8.7mm.
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