Question

cos 25 degrees * cos 65 degrees - sin 25 degrees * sin 65 degrees

Answer 1

Step-by-step explanation:

hey your answer is as follows

so pls mark it as brainliest

now according to complementary angle relation

we know that

sin(90-theta)=cos theta

cos(90-theta)=sin theta

so thus then

cos 25=

sin(90-25)=sin 65 degrees

also similarly cos 65=

sin(90-65)=sin 25 degrees

so substituting these values in cos 25 degrees× cos 65 degrees - sin 25 degrees×sin 65 degrees

We get

sin 65.sin 25-sin 65.sin 25

ie nothing but 0

so the answer of above trigonometric equation is 0 ie null