Question

Which equation is not an identity?

a. tan(–t) = –tan t
b. tan t(csc t + cot t) = sec t + 1
c. sin tcot t = cos t
d. cos2t − sin2t = –1

Answer 1

sin^2(x)+cos^2(x) = 1

multiply that by (-1) and check answer d

Answer 2

For C
\[\sin(t) \cot(t) = \sin(t)\frac{ \cos(t) }{ \sin(t) } = \cos(t)\]

true

Answer 3

the tangent of (-theta) is the same as (-1)tan(theta) by symmetry in the unit circle

Draw out both tan(-t) and -tan(t) with an arbitrary angle t, to see how they relate

Answer 4

I don't understand any of that...