[asy]
size(200);
pair A, B, C, D, E, F;
A = (0,0);
B = (1,0);
C = (0.5,0.866);
D = (0.5,0);
E = (0.5,-0.866);
F = (0.5,1.732);
draw(A--B--C--cycle);
draw(D--E);
draw(C--F);
label("$\theta_1$", (0.25,0.1));
label("$\Phi$", (0.5,0.9));
label("$n$",
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