Which of the following is not an identity?

A. 2sin^2 x - sinx = 1
B. secx cscx(tanx + cotx) = sec^2 x + csc^2 x
C. sin^2 x + tan^2 x + cos^2 x = sec^2 x
D. 2cos^2 x - 1 = 1 - 2sin^2 x

Question

Which of the following is not an identity?

 		A.	2sin^2 x - sinx = 1
 		B.	secx cscx(tanx + cotx) = sec^2 x + csc^2 x
 		C.	sin^2 x + tan^2 x + cos^2 x = sec^2 x
 		D.	2cos^2 x - 1 = 1 - 2sin^2 x

anonymous · Answer

graph each one use google and see if they intersect everywhere.

Hint: A is an ID I think.

anonymous · Answer

oh wait A might not be an ID :P

anonymous · Answer

https://www.google.com/search?rlz=1C1CHFX_enUS470US470&aq=f&sugexp=chrome,mod=8&sourceid=chrome&ie=UTF-8&q=2sin%5E2+x+-+sinx#hl=en&safe=off&rlz=1C1CHFX_enUS470US470&sclient=psy-ab&q=2*(sin(x))%5E2+-+sin(x)%2C1&oq=2*(sin(x))%5E2+-+sin(x)%2C1&aq=f&aqi=g-K1g-bK2g-bsK1&aql=&gs_l=serp.3..0i30j0i8i30l2j0i8i10i30.194699.194987.2.195240.2.2.0.0.0.0.161.288.0j2.2.0...0.0.xJb8XhPf4S0&pbx=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.,cf.osb&fp=43ca00f83d9a1a7e&biw=1024&bih=667