ABC is a right isosceles triangle right angled at B.Find cosA and sinA.
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draw a rough diagram
isosceles triangle <B =90
let AB = BC = x
AC =√AB²+BC²
AC =√x²+x²
AC =√2x²
AC =√2 *x
sinA = BC/AC =x/√2 *x = 1/√2
cos A = AB /AC = x/√2 *x = 1/√2
2) another method
<B =90
<A = <C =45[ isosceles triangles ]
sinA = sin45 = 1/√2
cos A = cos 45 = 1/√2
isosceles triangle <B =90
let AB = BC = x
AC =√AB²+BC²
AC =√x²+x²
AC =√2x²
AC =√2 *x
sinA = BC/AC =x/√2 *x = 1/√2
cos A = AB /AC = x/√2 *x = 1/√2
2) another method
<B =90
<A = <C =45[ isosceles triangles ]
sinA = sin45 = 1/√2
cos A = cos 45 = 1/√2
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