10 Points! What am I doing wrong? Physics hw q!

A narrow beam of ultrasonic waves reflects off the liver tumor in the figure below. If the speed of the wave is 5.5% less in the liver than in the surrounding medium, determine the depth of the tumor.

http://www.webassign.net/sercp9/22-p-022鈥?/a>

I got: 42.98. It says that is incorrect; what did I do wrong?

First find n鈧?using n=c/v

n鈧?= c/(1-0.055)c = 1.058

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Use Snell's Law to find 酶鈧?br>
n鈧?n鈧?= sin(酶鈧?/sin(酶鈧?

sin (酶鈧? = n鈧?n鈧?路 sin(酶鈧?

酶鈧?= sin鈦宦箋 1/(1.058) 路 sin(50潞) }

酶鈧?= 46.4潞

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Now it is a geometry problem

酶 = 46.4潞

adjacent side is unknown

opposite side is 6 cm (half the distance measured in diagram)

tangent = opposite/adjacent

tan(46.4潞) = 6/饾搷

饾搷 = 6/tan(46.4潞) = 5.7 cm