1) If the Sin(70 degrees)= Cos(A), what must A be?

2) Why is the Sine of 10 degrees the same as the Cosine of 80 degrees?

2 answers

20

the co- in cosine means sine of the complementary angle.

If cos(90-A) = cos90cosA + sin90sinA = sinA
cos 20

they are the same because they are complementary angles.

70 + 20 = 90
80 + 10 = 90