1. (1 - cos^2t / 1-sin^2t) + tgt*ctgt = 1 / cos^2t
sin^2t / cos^2t + 1 = (sin^2t + cos^2t) / cos^2t = 1 / cos^2t
1/cos^2t = 1/cos^2t
2. sint = -15/17
cos^2t = 1 - sin^2t = 1 - 225/289 = 64/289
cost = -8/17
tgt = sint/cost
tgt = 15*17/17*8 = 15/8
ctgt = 1/tgt = 8/15
Cos a=-√(1-sin²a)=-√(1- 1/3)=<em><u>-√(2/3)</u></em>
-1 ≤ arcCos4x ≤ 1 | +3
2 ≤ 3 + arcCos4x ≤ 4
0,04x^2 = 25
x^2 = 25/0,04
x = ± √ (25/0,04)
x = ± 5/0,2
x = ± 25
2xyz - 3x²z²+4xy³z=xz(2y-3xz+4y³)
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