Question

if sinA =a/b then find cos A

Answer 1

sin a=a/b
Hence cos a/b= √(1-sin^2a)=√(1-a/b^2)=√(b^2-a^2)/b

Answer 2

cos A =(1-sin^2 A)^(1/2)
cos A=(1-(a/b)^2)^(1/2)
cos A =(b^2-a^2)^(1/2)/b