Divide both sides by cos^2(theta): tan^2(theta)=1, so tan(theta)=+1. Theta=(pi)/4 (45 degrees), 3(pi)/4 (135°), 5(pi)/4 (225°), 7(pi)/4 (315°). These values are in consecutive quadrants where the tangent alternates between plus and minus 1. (QI, QIII are +1; QII, QIV are -1).