If cos alpha Squareroot 55 with 0 Solution13 cos a sqrt55

Solution

13) cos (a) = sqrt(5)/5 = 0.45,         sin (a) = 0.9

        cos (b) = -4/5 = 0.8,         sin (b) = 0.6

sin(a+b) = sin a cos b + cos a sin b = 0.9*0.8 + 0.45*0.6 = 0.99

14) cos (a) = 2/sqrt(5) = 0.9,         sin (a) = 0.44

       sin (b) = 1/sqrt(10) = 0.32,         cos (b) = 0.95

cos(a-b) = cos a cos b + sin a sin b = 0.9*0.95 + 0.44*0.32 = 0.9958

15)        sin (a) = -sqrt(3)/2 = 0.87,         cos (a) = 0.5

              cos (b) = 2/3 = 0.67,         sin (b) = 0.74

             tan (a) = 1.74,        tan (b) = 1.1

Tan(a-b) = (tan a tan b)/( 1 + tan a tan b) = 0.22