Find the exact value of cos(a+b) given that sin(a) = -1/2 with angle a in quadrant 4, and sin(b) = 1/4, with angle b in quadrant 2

The exact value of   cos (a + b ) is - 15.53°  

Step-by-step explanation:

Given as :

sin (a) = -

sin (b) =  

So, a = sin^{-1}(\frac{-1}{2})

i.e  a = -30°

And b = sin^{-1}(\frac{1}{4})

I.e b = 14.47°

Now, cos (a + b ) = cos (-30° + 14.47°  )

Or,    cos (a + b ) = - 15.53°

Hence The exact value of   cos (a + b ) is - 15.53°   Answer

18

step-by-step explanation: