Question

cos73+cos47-cos13
math

Answer 1

73

47. =133 total cost

+ 13

Answer 2

$\cos(a) + \cos(b) = 2 \cos( \frac{a + b}{2} ) \cos( \frac{a - b}{2} ) \\ cos60 = \frac{1}{2} \\ = > cos73 + cos47 - cos13 \\ = 2cos( \frac{73 + 47}{2} )cos( \frac{73 - 47}{2} ) - cos13 \\ = 2cos(60)cos(13) - cos13 \\ = cos13 - cos13 \\ = 0$

hope it helps