Quote: TanA=1/2,tanB=3/4,TanC=1/2,show that tan(A+B+C)=4/7
from wiki
let tan(A) = a, tan(B) = b, tan(C) = c
then
tan(A + B + C) = [size=150]([/size](a + b + c) - abc[size=150])[/size][size=150]/[/size][size=150]([/size]1 - (ab + bc + ac)[size=150])[/size]
so
tan(A + B + C) = [size=150]([/size](1/2 + 3/4 + 1/2) - 1/2*3/4*1/2[size=150])/([/size]1 - (1/2*3/4 + 3/4*1/2 + 1/2*1/2)[size=150])[/size]
tan(A + B + C) = [size=150]([/size]7/4 - 3/16[size=150])/([/size]1 - (3/8+3/8+1/4)[size=150])[/size]
tan(A + B + C) = (25/16)/(1-1)
which tries to divide by zero and is thus nonsense
are you sure you have your numbers right?
+6251 
