Several editions of Vance's books are available for free reading or borrowing through the : Modern Algebra and Trigonometry (1962) : Available for borrowing and streaming on Internet Archive Unified Algebra and Trigonometry
This requires algebraic manipulation (multiplying by conjugate) and domain reasoning — classic Vance. modern algebra and trigonometry vance pdf top
: Detailed exploration of Circular Functions , their applications to angles, and complex numbers. Several editions of Vance's books are available for