These expressions look complicated, but they are not if you know your trigonometric identities. Review the addition/subtraction formulas, double-angle formulas, and half-angle formulas in your Tool Kit. Then express each of the problems below in the form sin x or cos x. Homework Help ✎
sin 50°cos 20° + cos 50°sin 20°
Look in the index and/or glossary for these formulas.
Use the addition formula for sine.
sin(50° + 20°)
Use the sum/difference formula for the cosine. Be careful of your sign.
Use the Half-Angle Formula for cosine.
Use the Double-Angle Formula for the sine.
Use one of the Double-Angle Formulas for the cosine.
Use the Half-Angle Formula for sine.