Posted by **ken** on Friday, April 25, 2014 at 5:55am.

given that sin (2x+30)=cos(x-15).determine the value of x given x is an acute angle

- algebra -
**Steve**, Friday, April 25, 2014 at 6:13am
assuming that x is in degrees, then knowing that cos(x) = sin(90-x), we have

sin(2x+30) = sin(90-(x-15))

sin(2x+30) = sin(105-x)

so,

2x+30 = 105-x

3x = 75

x = 25

check:

sin(80) = cos(10)

yep.

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