3 years ago

Cos xcos y=1/2(sin(x+y)+ sin(x-y))

Mathematics

1 answer:

garri49 [273]3 years ago

7 0

Taking Rhs

1/2 [sin(x+y)+ sin (x-y)]

using sinA + sin B = 2 cos (A+B)/2 cos( A - B)/2

1/2 [ 2 Cos ( x+y+x-y)/2 . Cos (x+y-x+y)/2]

=Cos 2x/2. Cos 2y/2 = Cos x . Cos y

Hence true

You might be interested in

Please simplify this fraction c:

Liula [17]

F you just want to see the really short way, just skip down to AAAAAAAAAAAA

so, here is the long explanation
exponential properties
$x^{-m}= \frac{1}{x^m}$

don't forget pemdas
2x^2=2(x^2)

so
$\frac{2x^{-4}}{3xy}$ = $\frac{2 \frac{1}{x^4} }{3xy}= \frac{2}{3x^5y}$

AAAAAAAAAAAAAAAAAAAAAAAA
so we see
the original equatio is
$\frac{2x^{-4}}{3xy}$

remember
$\frac{ab}{cd} =( \frac{a}{c})( \frac{b}{d})$

so we can seperate the constants
$\frac{ab}{cd} =( \frac{2}{3})( \frac{x^{-4}}{xy})$

we know that the placeholders cannot affet the position of the constants unless they are grouped together which they are not

terfor the answer must have 2/3 in it

the only one that hsa that is A

ANSWER IS A

3 0

2 years ago

Read 2 more answers

Help ASAP , 15 points and a brainy.

Step2247 [10]

Answer:

Step-by-step explanation:

3 0

2 years ago

Read 2 more answers

PLEASE HELP LOOK AT THE PICTURE I NEED HELP NOWWWW!!!! WILL GIVE 20 POINTSSSSSS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Verdich [7]