Given that x is an obtuse angle and sin x =3/5, find, without the use of calculator, cos0.5x
please help me thanks. Also, i have something to clarify,in cases like this: solve for x between 0 to 180 deg
can i just cancel out cos x ? then i will have tan x =3/2 x=56.3
but since i cancel out the cos x so it is suppose to be zero so i just put cos x =0 and x=90
the zero part doesnt sound very logical to me.is it right to do that?
From the double angle formula :
cos 2a = 2cos^2a-1
Let a =x/2
cos x= 2cos^2(x/2)-1
Now , find
substitute x=143.13 and take the positive value .