Question

please do this question... ​

Answer 1

Answer of question no.19 and 20

Answer 2

Answer:

hello friend

i m solving question no. 18

if this answer will helpful for you then send more question related to trigonometry because i am found of trigonometry

Step-by-step explanation:

sin^4 A - cos^4 A = (sin²A)² - (cos²A)²

=(sin²A+cos²)(sin²A-cos²A)                              [by the formula of a²-b²]

=1(sin²A-cos²A)                                                 [by the formula of sin²+cos²=1]

=1[sin²A-(1-sin²A)]

=sin²A - 1+ sin²A

= 2 sin²A -1                   ...........(1)

=2(1-cos²A )-1

=2 - 2 cos²A-1

=2-1 - 2 cos²A

=1- 2 cos² A                                  ....................(2)

= 1- 2 cos²A

= 1- cos²A-cos²A

= sin²A-cos²A                             ...............................(3)

thanks