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

Tan(-t) =-tan(t) is correct

Tan(csc + cot) = (tan)(csc) + (tan)(cot)

= (sin/cos)(1/sin) + (sin/cos)/(cos)/(sin)

=(1/cos) +1 = sec(t) +1 so this is correct

(sin)(cot)= sin (cos/sin) = cos so this is correct

So that just leaves D which is not correct