求证1/(sin^2)a+1/(cos^2)a-1/(tan^2)a=2+(tan^2)a
问题描述:
求证1/(sin^2)a+1/(cos^2)a-1/(tan^2)a=2+(tan^2)a
答
左边=1/[(sin^2)a(cos^)a]-(cos^2)a/(sin^2)a=[1-(cos^4)a]/[(sin^2)a(cos^2)a]=[1+(cos^2)a] [1-(cos^2)a]/[(sin^2)a(cos^2)a]=[1+(cos^2)a]/(cos^2)a= [(sin^2)a+(cos^2)a+(cos^2)a]/(cos^2)a=[(sin^2)a+2(cos^2)a...