trigonometry question

Question

prove that

(1-tan²6)(1-tan²66)= -4

Answer 1

tan6 = .105

tan^2(6) = .011

tan^2(66) = 5.045

1-.011 = .989

1-5.045 = -4.955

.989x-4.955 = -4.9

maybe you typed 0 when you wanted 9? they're close on a keyboard

-4.0 instead of -4.9?