If angle Beta lies in quadrant II and sin Beta 513 determin

If angle Beta lies in quadrant II and sin Beta = 5/13 determine the value of cos 2B.

B is the symbol for beta.

Solution

Solution:

Sin(B) = 5/12

square on both side

sin²(B) = 25 /144

Now we know that

Cos(2x) = 1- 2sin² (2x)

therefore

Cos(2B) = 1-2(25/144)

Cos(2B) = 1 -25/72 = (72-25)/72

Cos(2B) = 47/72

Answer