Question

cos 33 cos 27-cos 57 cos 63 pls don't spam​

Answer 1

Answer:

Your answer is 1/2 = 0.5

Beforehand Knowledge : 1. 2cosAcosB = cosA + cosB.

2. cos(90+X) = -sinX.

3. cos(-X) = cosX.

Step-by-step explanation:

Let's begin.

cos33cos27 = (2cos33cos27)/2 = [cos(33+27) + cos(33-27)]/2

= [cos60 + cos6]/2. ..........{beforehand knowledge, point 1}

in a similar way, cos57cos63 = [cos(120) + cos(-6)]/2 .

Now, cos(-6) = cos(6)......... {beforehand knowledge , point 3}

so, finally, the entire expression reduces to

[cos60 + cos6]/2 - [cos120 + cos6]/2

or, [cos60 + cos120]/2 - [cos6 - cos 6]/2. .......《 cos6-cos6=0》

or, [(1/2)-(-1/2)]/2 - 0.......................{beforehand knowledge, point 2}

or, [(1/2)+(1/2)]/2 = 1/2 = 0.5

I'm also uploading the picture of my working, so that you can understand it better ...

Happy to help, from Kolkata(WB)