What is the exact value of Cos 135?

Solution:

Cos 135°= cos(90°+45°)

Now, take the values a = 90° and b = 45°

By using the formula, Cos(a+b) = cos a cos b – sin a sin b

So, it becomes Cos 135° = cos 90° cos 45° – sin 90° sin 45°

cos 135°=0 x 1/√2 – 1 x 1/√2

cos 135°=-1/√2

1 Comment

  1. wonderful!you used the simplest way

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