what is tan(4.2/6.5)

 tan(4.2/6.5)

 

I expect you mean

 

\(tan\theta = (4.2/6.5)\\ or\\ \theta=tan^{-1} (4.2/6.5) or\\ \theta=atan(4.2/6.5)\)

 

enter is as 

2nd  atan   (4.2/6.5)

makesure the calc is set to degrees