Question

Show that none of the following is an identity:
1. cos^2A+cosA=1
2. sin^2A+sinA=2
3. tan^2A+sinA=cos^2A​

Answer 1

Answer:

Let suppose that A = 0

so 1. LHS (cos0)^2 + cos0 = 1 + 1 = 2 which is not equals to RHS

2. LHS (sin0)^2 + sin0 = 0 + 0 = 0 which is not equals to RHS

3. LHS (tan0)^2 + sin0 = 0 + 0 = 0 which is not equals to RHS