Question

3（sin t）^2+(cost)^2怎么算出等于2-cos2t

Answer 1

2-cos(2t)

=2 - (1- 2(sint)^2 )

= 1 + 2(sint)^2

= (sint)^2+(cost)^2 +2(sint)^2

=3(sin t)^2+(cost)^2