1.

Simplify each of the following:`cos^(-1)(3/5cosx+4/5sinx)`, where `-(3pi)/4lt=xlt=pi/4`

Answer» `cos^-1 (3/5 cos x + 4/5 sin x)`
here, `cos alpha= 3/5`
`sin alpha = 4/5`
so,`cos^-1[cos alpha cos x + sin alpha sin x]`
`= cos^-1[ cos(x- alpha)]`
`x- alpha`
as`alpha = cos^-1 (3/5) = sin^-1(4/5) = tan^-1(4/3)`
so,answer=`x- tan^-1 (4/3)`


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