Question

1 1 Show that cos²@+2cos²@[1- 1/sec²@] is equal to= 1- sin²@​

Answer 1

Answer:

To prove:

1+2cos²A/1+3cot²A=sin²A

Consider

1+2cos²A/1+3cot²A

=1+2cos²A/1+3cos²A/sin²A

=sin²A(1+2cos²A/sin²A+3cos²A)

=sin² A(1+2cos²A/1-cos²A+3cos²A)

=sin² A( 1+2cos²A/1+2cos²A)

=sin² A