Question

sin(B-A) is equal to ??????? when B=270 degrees and A is an acute angle.

Answer 1

well sin 270-A=-cosA

Answer 2

?

Answer 3

its a way of converting to acute angles

Answer 4

hmm

Answer 5

so sin 270-A = cosA

Answer 6

Kindly explain......Im slow

Answer 7

Well when we know one angle is 270, it is in the third quadrant

Answer 8

Now 270 = 3x90

Answer 9

because 3 is odd, the name will change from sin to cos (for even numbers, it stays as the original)

Answer 10

In the third quadrant, cosine is negative

Answer 11

Do I need to prove? And are you using the pythagorean Identity?

Answer 12

no i am not, it is just the angle being in the third quadrant, no proving of pythagoreas is necessary

Answer 13

So which identity does it belong?

Answer 14

its not an identity, it is just conversion of an angle

Answer 15

here look at this picture