Verify the Given Identity $\cos ( x + y ) \cos ( x - y ) = \cos ^ { 2 } x - \sin ^ { 2 } y$

Q39: Simplify the following expression algebraically.​

Q40: Find the exact value of

Q41: Find the exact value of the

Q42: Find the exact value of the

Q43: Simplify the expression algebraically.​ <span

Q45: Write the given expression as the

Q46: Find the exact value of

Q47: Find the exact value of the

Q48: Simplify the expression algebraically.​ <span

Q49: Find the exact solutions of the