## Dallasb22 3 years ago Find the area of the Trapezoid?

1. Dallasb22

2. Dallasb22

A=(_√_) divided by _

3. Dallasb22

@Hero help?

4. Dallasb22

@lgbasallote help?

5. lgbasallote

|dw:1348069206419:dw| do you know how to find x?

6. Dallasb22

Ah i believe so.

7. Dallasb22

Actually i am brain frozen and cannot remember the formula. Can you tell me the formula please?

8. tyteen4a03

The formula for tan x is opp/adj. The formula for finding the area of a trapezoid is ((upper length + lower length) * height)/2.

9. Dallasb22

Finding X in his above drawing would give me the height so i could than find the area.

10. Dallasb22

But I do not remember how to find it. I have never used tan or sin before.

11. Dallasb22

|dw:1348069912936:dw|

12. Dallasb22

@tyteen4a03

13. tyteen4a03

Were you taught trigonometry (sin, cos, tan) in your math lessons?

14. Dallasb22

I am only in Geometry, so not yet.

15. tyteen4a03

This question involves trigonometry... I will just give you a crash course. For the triangle |dw:1348070256213:dw| (do notice that these formulas only work on triangles with a right angle), we pick a angle that is not the right angle itself. This time, I pick <AC. (answers continued since I can't see what I just drew)

16. Dallasb22

Ok

17. tyteen4a03

uh... I meant <C. Anyways, we usually represent angles with the symbol theta ($$\theta$$). Remember these properties: (all of these are lengths of the said line) sin $$\theta$$ = opposite/hypotenuse (sine) cos $$\theta$$ = adjacent/hypotenuse (cosine) tan $$\theta$$ = opposite/adjacent (tangent) What is opposite and what is adjacent in here? Notice that the angle <C is opposite of the line AB, so that is the opposite line. The <C is adjacent (or in other terms "sticks") to the line BC, so that's the adjacent. Let's look back at the question bit @Igbasallote asked you to solve. Here, tan$$\theta$$ = x/3 (opposite/adjacent). Multiply both sides by 3, and get 3 tan$$\theta$$ = x. It also specified that the angle is 60 degrees. I'll give you the answer here: tan 60degrees = $$\sqrt{3}$$. Now multiply the answer by 3, and the answer becomes $$3\sqrt{3}$$. Congrats, you just learnt pieces your classmates might've never learned. However, I suggest telling your teacher that you haven't learned trigonometry yet so he/she will not give you these kind of questions.

18. tyteen4a03

(Just that if you're curious how I pulled tan 60degrees out of the air, 60 degrees is actually a special angle. You can find the values of trigonometry function on special angles here: http://www.mathwords.com/t/trig_values_of_special_angles.htm )

19. Dallasb22

Okay i think i got it. Yes i know the triangle ratio 30-60-90