Question

What's the relationship between sine and cosine of complementary angles

Answer 1

sin x = cos (90 - x)

cos x = sin(90 - x)

Answer 2

Thank you!

Answer 3

Here is a reminder.

Triangle ABC is a right triangle with right angle C.
That means angles A and B must be complementary.

Answer 4

Using the trig ratios, we get:

\(\sin A = \dfrac{y}{h}\)

\(\cos B = \dfrac{y}{h}\)

We can write

\(\sin A = \cos B\)

Since angles A and B are complementary, we have

A + B = 90

or

B = 90 - A, so we end up with

\(\sin A = \cos (90 - A)\)