D. Convert each expression into a product and simplify if possible. 11. cos50' - cos 10 12. sin= + sin 10 E. Simplify: 13. 1+cos20 sin20 14. tanosin20 15. Prove tan80 (1 - tan249) = 2tan40C. Express the following as a sum or difference of sine and cosine. 1 1. cos40' sin10 12. 4cos 70cos 50 D. Express the following as a product of sine and cosine. 13. sin24' + sin(-4") 14. cos3x - cos9x 15. Simplify: sin4x cos2x