Trig Question

Find x where arc denotes the principal value.
x= cos(arcsin(4/5)+arctan(4/5))

x=-.031234752378

did you use a calculator?show me the math!lol

Nobody answered this question either?

-sqrt(41)/205

post your proof

let

sin a =4/5
tg b=4/5

cos(a+b)= cos a cos b - sin a sin b

sin a = 4/5 => cos a = 3/4

sin b = 4/5 cos b
sin ^2 b + cos^2 b = 16/25 cos^2 b + cos^2 b =1

41/25 cos^2 b= 1

cos^2 b= 25/41

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