Trigonometry/Proof of special trig values

In this book, you will learn the proofs of the simple and familiar trig values for special angles.

Proof that tan(45 degrees) = 1




Start with a square, as shown in the first image to the right. Draw the diagonal of the square by using a straight line to connect the upper right vertex with the lower left vertex, as shown in the image below.

Proof that cos(60 degrees)=0.5


Start with a right triangle. Draw a perpendicular line from the top vertex to the midpoint of the low base, as shown in the image to the right. That line bisects the low base, BC, into two equal segments.