how to exact value of sin(cos^-1(4/5)) ?

Question

anonymous · Answer

im not sure what ur saying ??

hero · Answer

I'll see what I can do to help you

anonymous · Answer

ok...:)

anonymous · Answer

sr but i dont get where you got pi in "cosine 4pi/5" ?

anonymous · Answer

ok lets redo it, may be i copied the incorrect data

anonymous · Answer

lets inverse cosine 4/5=y
so you have cos y= 4/5, find sin y,

your original question was sin(inverse cosine 4/5)= sin (y)

anonymous · Answer

makes sense?

anonymous · Answer

thats the exact value ?

anonymous · Answer

you need to find sin 4/5, if you have a calculator

anonymous · Answer

im not allowed to use calculator

anonymous · Answer

is there anyway that i can find the value without calculator ?

anonymous · Answer

unfortunately not, well the closed we can it convert to radians by multiplying 4/5 with pi/180

hero · Answer

@psi9epsilon it's already in radians

anonymous · Answer

@hero, sorry i did not read it was in radians, well then that all about it, unless you want to convert it to degrees by multiplying with 180/pi

hero · Answer

Doing that won't help to find the exact value

anonymous · Answer

thats what I was trying to say, you cant get more out of sin (4/5) without a calculator

anonymous · Answer

@hero, do you disagree with the method, if so, kindly show an interesting solution , i am eager to learn : )

hero · Answer

Apparently you're supposed to use pythagorean trig identity to do it

zepdrix · Answer

oo oh oh oh that makes sense :O

zepdrix · Answer

|dw:1348690766838:dw|
interesting c: