Question

докажите тождество $1+ctg^2a+\frac{1}{cos^2a} =\frac{1}{sin^2a cos^2}$

Answer 1

(1+ctg^2 a)+ 1/ cos^2 a= 1/sin^2 a +1/cos^2 a= sin^2 a+cos^2 a/ sin^2 a* cos^2 a= 1/ sin^2 a* cos^2 a