यदि `(mtan(alpha-theta))/(cos^(2)theta)=(ntantheta)/(cos^(2)(alpha-theta))` है तो सिद्ध कीजिए कि
`2theta=alpha-tan^(-1)[(n-m)/(n+m)tanalpha]`

Answer

`alpha-tan^(-1)[(n-m)/(n+m)tanalpha]`