Write $\cos ( \beta - \alpha ) \cos \alpha$ As a Sum

Q87: Verify the identity. <span class="ql-formula"

Q88: Verify the identity. <span class="ql-formula"

Q89: Use a double-angle formula or a

Q90: Write the sum as a product.

Q91: Solve the given equation. <span

Q93: Use addition or subtraction formulas to

Q94: Solve the given equation. <span

Q95: Use a double-angle formula or a

Q96: Solve the given equation. <span

Q97: Find <span class="ql-formula" data-value="\sin 2