Trigonometry
posted by Kayla on .
Write the expression as a trigonometric function of one number.
(cos 20 degrees)(cos 70 degrees)+(sin 20 degrees)(sin 70 degrees)

Have you come across the identity
cos(AB) = cosAcoB + sinAsinB ?
your question fits that pattern perfectly.
Let me know what you get. 
ok I made a mistake in the formula. it's cos(20 degrees)cos(70 degrees) sin(20 degrees) sin(70 degrees).
so it's a subraction equation not an addition. 
and of course there is the matching formula for
cos(A+B) = cosAcosB  sinAsinB
So what do you think? 
so it would be cos(20+70)?

cos(20 degrees+70 degrees) i mean

yes, but what is cos(20° + 70°) ??
= cos 90°
= 0
so your
cos(20 degrees)cos(70 degrees) sin(20 degrees) sin(70 degrees)
= 0 
Yeah I got the exact value I just needed it in trigonometric function of one number which would be the degrees of cos.
Thanks!!! 
HELP ME !
sin50 cos 20  cos 50 sin 20
^find exact value 
Pls tell me how to find out sin70.Pls

How are the sun 70 degrees and cos 20 seg related