30 - 60 - 90 Triangles And You!
Remember the Pythagorean Theorem? The sum of the square of the legs is equal to the square of the hypotenuse. a 2 + b 2 = c 2 30 60 a b c
Solve for the missing side! a 2 + b 2 = c 2 30 60 3 b b 2 = b 2 = 36 b 2 = 27 b = 27 b = 3 3 First we need the Pythagorean Theorem! Square the numbers! Substitute the correct values! Subtract 9 on both sides! Take the square root on both sides! Simplify the square root!
That’s a lot of work for one answer!
Wouldn’t it be nice if there was a faster and shorter way!?!
But where do we start? 30 60 3 6 3
Let’s identify the sides of a 30 -60 -90 triangle 30 60 Hypotenuse The longest side located across the right angle!
Let’s identify the sides of a 30 -60 -90 triangle 30 60 Hypotenuse Long Leg The side located across the 60 angle!
Let’s identify the sides of a 30 -60 -90 triangle 30 60 3 6 Hypotenuse Short Leg Long Leg The shortest side located across the 30 angle!
30 60 3 6 Hypotenuse Short Leg Long Leg It’s very important to remember where the sides are located!!
Let’s look back at the original problem! 30 60 Notice how the hypotenuse is twice as big as the short side! Hypotenuse = Short Leg x 2 Hypotenuse = 3 x 2 Hypotenuse = 6
30 60 Now, compare the short leg with the long leg! Long Leg = Short leg x 3 Long Leg = 3 x 3 Long Leg = 3 3 Notice how the long leg equals the short leg multiply by the square root of three!
30 60 3 Short Leg So, if you know the value of the short leg, then you can figure out the other two sides! Hypotenuse = Short Leg x 2 Long Leg = Short leg x 3
Let’s try a couple of problems! 30 60 7 c b Short Leg = 7 Hypotenuse = Short Leg x 2 Hypotenuse = 7 x 2 Hypotenuse = 14 Long Leg = Short leg x 3 Long Leg = 7 x 3 Long Leg = 7 3
Try this one! 30 60 9 c b Short Leg = 9 Hypotenuse = Short Leg x 2 Hypotenuse = 9 x 2 Hypotenuse = 18 Long Leg = Short leg x 3 Long Leg = 9 x 3 Long Leg = 9 3
30 60 3 Short Leg Remember, the following formulas only occur in a 30 -60 -90 triangle! Hypotenuse = Short Leg x 2 Long Leg = Short leg x 3
THE END!