Revision of Trigonometry

Revision of Trigonometry

Revision for GCSE Maths

Multiple Choice

We can use SOH-CAH-TOA for...

• Any triangle ever

• Non-right triangles only

• Right Triangles only

• Never

Multiple Choice

Identify the hypotenuse.

• a
• b
• c

Multiple Choice

The side labelled as "c" is called the

• Opposite

• Adjacent

• Hypotenuse

Multiple Choice

The side labelled as "a" is called the

• Opposite

• Adjacent

• Hypotenuse

Multiple Choice

The side labelled as "b" is called the

• Opposite

• Adjacent

• Hypotenuse

6 Steps to finding an angle

• Step 1 - Label the sides

• Step 2 - Choose the trig ratio that you want to use

• Step 3 - Write the trig ratio down with the thing you want find as the subject

• Step 4 - Substitute in the numbers that you have

• Step 5 - Rearrange so that you put sin^-1 or cos^-1 or tan^-1 on the other side

• Step 6 - Calculate your answer

Step 1

• Copy the triangle down

• Label the sides

Multiple Choice

What side is the 25cm?

• Opposite

• Hypotenuse

• Anjacent

• I don't know how to work this out

Multiple Choice

What side is the 16cm?

• Opposite

• Hypotenuse

• Anjacent

• I don't know how to work this out

Multiple Choice

Which side do we know nothing about and wish to know nothing about?

• Opposite

• Hypotenuse

• Anjacent

• I don't know how to work this out

Step 2

• Choose which formula triangle you need to use

Multiple Choice

Which formula triangle do we need to use for this example?

• SOH

• CAH

• TOA

• I don't know how to work this out

Step 3

• Write the formula with what you want to find at the subject

Multiple Choice

How should you write the formula down?

• $\sin\ \theta\ =\ \frac{Opp}{Hyp}$

• $\cos\ \theta\ =\ \frac{Adj}{Hyp}$

• $\tan\ \theta\ =\ \frac{Opp}{Adj}$

• I don't know what's going on

Step 4

• Substitute in the numbers

Multiple Choice

What should the formula look like now?

•  $\cos\ \theta\ =\ \frac{25}{16}$ 

•  $\cos\ 16\ =\ \frac{\theta}{25}$ 

•  $\cos\ \theta\ =\ \frac{16}{25}$ 

• I don't know what's going on

Step 5

• Rearrange so that the angle is the subject of the formula.

Multiple Choice

What should the formula look like now?

•  $\theta\ =\ \cos^{-1}\frac{25}{16}$ 

•  $\theta\ =\cos^{-1}\ \frac{16}{25}$ 

•  $\theta\ =\ \sin^{-1}\frac{16}{25}$ 

• I don't know what's going on

Step 6

• Put it in the calculator to work out the angle.

• Give your answer to 1 decimal place

Multiple Choice

What answer do you get?

• 50.2

• 39.8

• 53.1

• I don't know what's going on

5 Steps to finding a side

• Step 1 - Label the sides

• Step 2 - Choose the trig ratio that you want to use

• Step 3 - Write the trig ratio down with the thing you want find as the subject

• Step 4 - Substitute in the numbers that you have

• Step 5 - Calculate your answer

Step 1

• Copy the triangle down

• Label the sides

Multiple Choice

What side is the opposite?

• 8

• x

• 29^o

• I don't understand

Multiple Choice

What side is the adjacent?

• 8

• x

• Doesn't have a number on

• I don't understand

Multiple Choice

What side is the hypotenuse?

• 8

• x

• Doesn't have a number on

• I don't understand

Step 2

• Choose which formula triangle you are going to use.

• Remember you need to cross out the side that you don't have any information about and don't wish to know anything about.

Multiple Choice

Which formula triangle are you going to use?

• I don't understand

Step 3

• Write the unknown as the subject of the formula

Multiple Choice

How should you have written the formula down?

• $opp\ =\ \frac{\sin\theta}{hyp}$

• $opp\ =\ \sin\theta\times hyp$

• $\sin\ \theta=\frac{opp}{hyp}$

• I don't understand

Step 4

• Substitute in the numbers

Multiple Choice

What should the formula look like with the numbers in?

•  $x\ =\ \frac{\sin29}{8}$ 

•  $x\ =\ \sin\ \frac{8}{29}$ 

•  $x=\sin\ 29\ \times8$ 

• I don't understand

Step 5

• Do the calculation.

Multiple Choice

What answer do you get, to 2 decimal places?

• 3.88

• 3.87

• 12.38

• I don't understand

Poll

Let me know how you feel about this topic.

Red - really don't understand

Amber - kinda ok but need some practise

Green - yes I've got this

• Red

• Amber

• Green