Posted by **shan** on Saturday, September 6, 2008 at 4:04pm.

tanx+secx=2cosx

(sinx/cosx)+ (1/cosx)=2cosx

(sinx+1)/cosx =2cosx

multiplying both sides by cosx

sinx + 1 =2cos^2x

sinx+1 = 2(1-sin^2x)

2sin^2x + sinx-1=0

(2sinx+1)(sinx-1)=0

x=30 x=270

but if i plug 270 back into the original equation i get undefined because tan 270 is undefined where did i go wrong?

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