u/Studbeastank

Hi all, I am studying for the PE and am very confused. I looked up Nordlund method for a problem requesting skin friction/uplift capacity in the NCEES Geotech practice exam and followed FHWA - NHI - 06-088 closely and got it wrong. I noticed FHWA - NHI - 06-088 has a sine function in the equation, however the solution indicates that you are supposed to use tangent. Which one is correct? Does the practice exam have a mistake in the solution or if not, where do I find the equation with tangent function in it in my references?

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