6. If f(m_1) = m_1-1 / m_1+1, show that

f(m_1)-f(m_2) / 1+f(m_1)f(m_2) = m_1-m_2 / 1+m_1m_2.

7. If \phi(x) = a^x, show that \phi(y) . \phi(z) = \phi (y + z).

8. Given \phi(x) = log 1-x / 1+x; show that

\phi(x)+\phi(y) = \phi (x+y / 1+xy).

9. If f(\phi) = cos \phi, show that

f(\phi) = f(-\phi) = -f(\pi - \phi) = -f(\pi + \phi).

10. If F(\theta) = tan \theta, show that

F(2\theta) = 2F(\theta) / 1-[F(\theta)]^2.

11. Given \psi(x) = x^2n + x^2m + 1; show that

\psi(1) = 3, \psi(0)=1, \psi(a) = \psi(-a).

12. If f(x) = 2x-3 / x+7, find f($$2). Ans. -.0204.
