Question

find the value of cos -3 pie by 4​

Answer 1

Answer:

1/√2

Step-by-step explanation:

cos(-3π/4)

cos(-135)

0.707

cos(-3π/4)=1/√2

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Answer 2

Answer:

answer is -1/√2

Step-by-step explanation:

cos(-3π/4)

when we convert it into degree then

-3π/4 ×180°/π = -135°

now

means angle lies in 2nd quadrant ,and we know that cos thitha in 2nd quadrant is negative

so (180°-135°)

= 45°

cos45° (in second quadrant cos thitha is negative)

so -1/√2.

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