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Week 17- Trigonometry

This week we learned how to do some trigonometry and refresh some ideas from last year.

Before you do anything put down the three diagrams:

Also write down Soh Cah Toa, which can also be S\frac{y}{r} C\frac{x}{r} T\frac{y}{x}

SINE LAW: Now when using sine law to find a side you must use this formula \frac{sinA}{a}=\frac{sinB}{b}=\frac{sinC}{c} if you want to find an angle you just flip the fractions over.

Ex:

 

to find the angle you use the formula of \frac{sinA}{a}=\frac{sinB}{b}

then plug in the numbers

\frac{sin50}{20}=\frac{sinB}{17}

which finally gives you $latex \angleB=41

COSINE LAW: When using Cosine law if you want to find the side you want to use the formula a^2=b^2+c^2-2bcCOSA if you want to find the \angle You must use the formula COSA=\frac{b^2+c^2-a^2}{2bc}

Ex:

 

To find f you use the given formula a^2=b^2+c^2-2bcCOSA

then plug in the numbers

a^2=21.3^2+30^2-2(21.3)(30)cCOS74 \sqrt{a^2}=\sqrt{1001}

finally you get the answer of a=31.6

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