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Here. You must know the values of the sine, cosine and tangent of the special angles.

Date Posted:
1 week ago

Should you forget the special angles during test, use calculator to help you recall.

Square the value to see what fraction you get.

For example ,

keying sin60° into calculator gives you 0.866025404. just from looking, you can't really tell what its exact form is.

Immediately square this value by pressing the x² function on your calculator.

You would see 0.75 or ¾

Now since the square of sin60° is ¾, and sin60° is positive,

then sin60° is just √(¾) = √3/2

It's also useful for other angles

Eg. sin 225° gives you -0.707106781

Squaring immediately gives 0.5 or ½

Since the square of sin225° is ½, and

sin225° itself is negative,

Then sin225° = -√(½) = -1/√2