# trig

posted by Pallav

tan200(cot10-tan10)

1. Reiny

keystrokes I used on my SHARP scientific calculator

I assume your units are degrees, so make sure your calc is set to DEG

tan 10
-
tan 10 =
x
ta200
=

you should get 2

2. Reiny

proof of above:

tan200(cot10-tan10)
= tan20(1/tan10 - tan10) , 9since by CAST tan200 = tan200)
= tan20( 1 - tan^2 10)/tan10
= 2tan10/(1 - tan^2 10) * ( 1 - tan^2 10)/tan10
= 2

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