Prove $\cos \left( x + \frac { \pi } { 4 } \right) = - \sin \left( x - \frac { \pi } { 4 } \right)$

Q5: Find all solutions of <span

Q6: Write <span class="ql-formula" data-value="\sin ^

Q7: Use a double-angle formula or a

Q8: Find the exact value of the

Q9: Find all solutions of <span

Q11: Use addition or subtraction formulas to

Q12: Simplify the trigonometric expression. <span

Q13: Simplify. <span class="ql-formula" data-value="\frac {

Q14: Use a graphing device to find

Q15: Solve the given equation. <span