(1) sec(x)-cos(x)=a3, csc(x)-sin(x)=b3;
(1-cos2(x))/cos(x)=a3, (1-sin2(x))/sin(x)=b3;
sin2(x)/cos(x)=a3; cos2(x)/sin(x);
(sin2(x)/cos(x))(cos2(x)/sin(x))=a3/b3;sin3(x)/cos3(x)=a3/b3.
Take cube root of each side: sin(x)/cos(x)=tan(x)=a/b QED
(2) (tan(P)-1)/(1+tan(P))=tan(195);
tan(P)-1=tan(195)+tan(P)tan(195);
tan(P)-tan(P)tan(195)=1+tan(195);
tan(P)=(1+tan(195))/(1-tan(195))=
(tan(45)+tan(195))/(1-tan(45)tan(195)=
tan(45+195); so P=240°.
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