- Similarly, cosine is , so if cos x = 0.6, then . Multiply both sides by 10 to
determine the side adjacent to the angle with measure x° is 6. With those two sides, find the area. The
formula for area is A = bh, so A = (6)(8) = 24, which is (C).
Pythagorean Theorem
The Pythagorean Theorem states that in a right triangle, the square of the hypotenuse equals the sum of the
squares of the other two sides. As we told you earlier, the hypotenuse is the longest side of a right
triangle; it’s the side opposite the right angle. The square of the hypotenuse is its length squared. Applying
the Pythagorean Theorem to the following drawing, we find that c^2 = a^2 + b^2.
Pythagorean Theorem
a^2 + b^2 = c^2 , where c is
the hypotenuse of a right
triangle. Learn it; love it.If you forget the Pythagorean Theorem, you can always look it up in the box at the beginning of the Math
sections.
ETS loves to test the Pythagorean Theorem along with SOHCAHTOA. See the following sample
question.
15.In ΔABC (not shown), AC BC and cos ABC = . What is the value of tan ABC ?