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The cos value when angle of a right triangle equals to $90^°$ is called cosine of angle $90$ degrees. Mathematically, it is written as $\cos{(90^°)}$ as per sexagesimal system.

$\cos{(90^°)} \,=\, 0$

The cosine of angle $90$ is exactly equal to zero and it is often called as trigonometric ratio (or function) of standard angle.

Alternative form

The $\cos{(90^°)}$ can be written alternatively in two different forms. It is written as $\cos{\Big(\dfrac{\pi}{4}\Big)}$ in circular system and also written as $\cos{(100^g)}$ in centesimal system.

$(1) \,\,\,$ $\cos{\Big(\dfrac{\pi}{2}\Big)} \,=\, 0$

$(2) \,\,\,$ $\cos{(100^g)} \,=\, 0$

Proof

Now, learn how the exact value of cos of angle $90$ degrees is equal to zero mathematically in trigonometry.

Ashok Kumar, B.E.

Founder of Math Doubts

A Specialist in Mathematics, Physics, and Engineering with 14 years of experience helping students master complex concepts from basics to advanced levels with clarity and precision.

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