Finding stress components from Mohr's circle with 100° rotation

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Blugga
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Homework Statement



Plane stress in xy-plane. Use Mohr's Circle to find σx1 σy1 and τx1y1 if the XY axis is rotated counterclockwise θº

I want to do my HW problem myself so I'll just put some sample values. If i know how to get this one, i'll know how to do the HW problem(s).
(Units won't matter for this)

σx = -45
σy = -15
τxy = -20 which makes τyx = 20
θ = 100°

Homework Equations


τmax=R
R = √((σx-σy)/2)2+τxy2
center=σave= (σx+σy)/2


The Attempt at a Solution


center=σave= {[(-45)+(-15)]/2} = -30
R=25
Point A (-45,-20)
Point B (-15,20)
Using my book (Gere 8th), i was only able to get this far. Not sure if this is on the right track or not, but I'm stuck at this point. Don't know how to continue...
How can I get σx1 σy1 and τx1y1 from here?
Mohr's circle diagram with center C, a red diameter from A (θ=0°) to B (θ=90°), and a blue radius from C to D and D' at a 20° angle, with a curved arrow labeled 2θ between the two diameters.
 
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