Question

which of the following are identities?
a. sin8x = 2sin4x cos4x
b.(sinx-cosx) ^2 = 1 + sin2x
c. (1-tan^2x)/2tanx = 1/ tan2x
d. (sinx +sin5x)/ (cosx+ cos5x) = tan3x

Answer 1

just put in a value for x and see if it is true.

Answer 2

i can't do c

Answer 3

whenever i try to input values it never works

Answer 4

.

Answer 5

that was helpful

Answer 6

XD

Answer 7

can you please help me ?

Answer 8

The answer can't B
(sinx - cosx)^2 = (sinx)^2 - 2sinxcosx + (cosx)^2
(sinx)^2 + (cosx)^2 = 1; 2sinxcosx = sin2x

therefore,
(sinx - cosx)^2 = 1- sin2x

Answer 9

Answer is A
http://www.wolframalpha.com/input/?i=+sin8x+%3D+2sin4x+cos4x

Answer 10

a ..... not b ..okay what about c and D?

Answer 11

c. correct to

Answer 12

d. correct