Use an Addition or Subtraction Formula to Write $\cos 75 ^ { \circ } \cos 15 ^ { \circ } + \sin 75 ^ { \circ } \sin 15 ^ { \circ }$

Q72: Use an addition or subtraction formula

Q73: Simplify. <span class="ql-formula" data-value="\frac {

Q74: Use a half-angle formula to find

Q75: Verify the identity. <span class="ql-formula"

Q76: Find all solutions of <span

Q78: Simplify. <span class="ql-formula" data-value="\frac {

Q79: Solve the given equation. <span

Q80: Use an addition or subtraction formula

Q81: Write the sum as a product.

Q82: Solve the given equation. <span