Question

If sin(90 degree-a)=BC/CA, write down the ratio of sina

Answer 1

Step-by-step explanation:

It’s cos(A).

This is how to prove it:

sin(90∘−A)

Use the following identity: sin(s−t)=−cos(s)sin(t)+cos(t)sin(s)

So now we have =−cos(90∘)sin(A)+cos(A)sin(90∘)

Solving for cos(90∘)sin(A).

Using the following identity: cos(90∘)=0

=0⋅sin(A)=0

Solving for: cos(A)sin(90∘)

Using the following identity: sin(90∘)=1

=1⋅cos(A)=cos(A)

So combining: −0+cos(A)=cos(A)

=cos(A)