Problem: In the right triangle shown the sum of the distances B M B MB M and M A M AM A is equal to the sum of the distances B C B CB C and C A C AC A . If M B = x , C B = h M B=x, C B=hM B = x , C B = h , and C A = d C A=dC A = d , then x xx equals:
Answer Choices:
A. h d 2 h + d \dfrac{h d}{2 h+d}2 h + d h d ​
B. d − h d-hd − h
C. 1 2 d \dfrac{1}{2} d2 1 ​ d
D. h + d − 2 d h+d-\sqrt{2 d}h + d − 2 d ​
E. h 2 + d 2 − h \sqrt{h^{2}+d^{2}}-hh 2 + d 2 ​ − h
Solution:
x + d 2 + ( h + x ) 2 = h + d , d 2 + ( h + x ) 2 = h + d − x x+\sqrt{d^{2}+(h+x)^{2}}=h+d, \sqrt{d^{2}+(h+x)^{2}}=h+d-xx + d 2 + ( h + x ) 2 ​ = h + d , d 2 + ( h + x ) 2 ​ = h + d − x d 2 + h 2 + 2 h x + x 2 = h 2 + d 2 + x 2 + 2 h d − 2 h x − 2 d x , 2 h x + d x = h d ; d^{2}+h^{2}+2 h x+x^{2}=h^{2}+d^{2}+x^{2}+2 h d-2 h x-2 d x, 2 h x+d x=h d ;d 2 + h 2 + 2 h x + x 2 = h 2 + d 2 + x 2 + 2 h d − 2 h x − 2 d x , 2 h x + d x = h d ; ∴ x = h d / ( 2 h + d ) \therefore x=h d /(2 h+d)∴ x = h d / ( 2 h + d ) .