Arthur D. answered 10/29/19
Forty Year Educator: Classroom, Summer School, Substitute, Tutor
I'm going to leave out Θ to make it easier to write.
tan+sec=cos/(1-sin)
(sin/cos)+(1/cos)=(cos)/(1-sin)
(sin+1)/(cos)=(cos)/(1-sin) cross multiply or multiply both sides by (cos)(1-sin) to get...
(sin+1)(1-sin)=(cos)(cos)
(1+sin)(1-sin)=(cos)(cos)
1-sin^2=cos^2
1=sin^2+cos^2 (true trig identity)
tan^2-sin^2=sin^2tan^2
(sin^2/cos^2)-sin^2=sin^2tan^2
(sin^2/cos^2)-(sin^2cos^2/(cos^2)=sin^2tan^2
(sin^2-sin^2cos^2)/(cos^2)=sin^2tan^2
[(sin^2)(1-cos^2)]/(cos^2)=sin^2tan^2
[(sin^2)/(cos^2)](1-cos^2)=sin^2tan^2
tan^2sin^2=sin^2tan^2 because tan=sin/cos and sin^2+cos^2=1 which means sin^2=1-cos^2