Question

sin²a(1+ctg²a)-cos²a​

Answer 1

Ответ:

${ \sin( \alpha ) }^{2} (1 + { \cot( \alpha ) }^{2} ) - { \cos( \alpha ) }^{2} = { \sin( \alpha ) }^{2} + { \sin( \alpha ) }^{2} \ \times \frac{ { \cos( \alpha ) }^{2} }{ { \sin( \alpha ) }^{2} } - { \cos( \alpha ) }^{2} = { \sin( \alpha ) }^{2} + { \cos( \alpha ) }^{2} - { \cos( \alpha ) }^{2} = { \sin( \alpha ) }^{2}$