Question

Find the value of cos 135º.​

Answer 1

The exact value of cos(135°) is -√(2) / 2.

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Answer 2

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Cos135°

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Explanation:

$= > Cos135 °= cos(180 - 135)$

$= Cos45° = - \frac{1}{ \sqrt{2} }$

$= > Cos135 °= - \frac{1}{ \sqrt{2} }$

Reason :why cos 135° is negative..??

• Cos 135° is an angle which lies in the second quadrant and in the second quadrant Cos is negative.lets see figure 1.1 above attached:

Tricks to learn figure 1.1 table :

• Add:$\bold{\red{All +ve}}$
• sugar:$\bold{\red{sin +ve}}$
• To:$\bold{\red{Tan +ve}}$
• Coffee:$\bold{\red{Cos +ve}}$

Additional information:

• Cos and sin completes it's angle of revolution after an interval of 2π
• Tan completes its angle of revolution after an interval of π

Remember:

=>The value of cos ,sin changed at 90°,270°