Find the exact value of each expression, leaving your answer in surd form where necessary: (a) cos 40° cos 50° – sin 40° sin 50° (b) sin 37° cos 7° – cos 37° sin 7° i wish to know how we find the values of non special trigonometric angles like 15 , 25 ,1 7 like dat?

Mrs. avila is buying a wallpaper border to go on all of her kitchen walls. she wants to buy 5 extra feet of wallpaper border than she needs to be sure she has enough. she buys 55.5 feet of the border. the store owner selling the border uses the width of mrs. avila's kitchen to determine that the length of her kitchen must be 14.5 feet.