Need Help with Trig?

I have a few trig questions I'm just not sure and/or don't understand.





1) tan θ =.5890 in Q1


2) 390°= ?? what in rad.


b) reference angle = ??what in deg.


c) reference angle= ?? what in rad.


3) 4 cos (-π/4)


4)sin 3x if x=π/6





I have these answered but I'm not sure if I have them right. PLEASE HELP!! thanks.

Need Help with Trig?
1)tan θ =.5890 ----%26gt; θ=30.498 deg.





2) 390° =?? in rad.


rule Ar/π =Ad/180 (where Ar is the angle in rad. %26amp; Ad is the angle in deg.)


so Ar=π*390/180=3.14159 * 390/180=6.806784





b) 390°----%26gt;390-360=30° (subtract 360 until the number between 0-360)


c)30°===%26gt;π*30/180=0.523599 in rad





3) 4 cos(-π/4)


as a fact π----%26gt; 180° so π/4----%26gt;45°


cos(x)=cos(-x)


so 4cos(-π/4)= 4cos(-45°)= 4cos(45°)= 4sqr(2)/2= 2sqr(2)


=2.82842712





4sin 3x if x=π/6


sin(3π/6)= sin(π/2)=sin90°=1
Reply:t=0.5323 rad


2) 390/x=360/2pi so x= 390/360 * 2p=2.1667 pi


b)360 degrees and 2pi rad


4cos(-pi/4)= 4 cos pi/4 = 2*sqrt(2)


sin 3x = sin pi/2= 1

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