SOH CAH TOA

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SOH CAH TOA

Find angle C. Give your answer correct to 1 dp.

Answer

We have been given the lengths of AC and BC and asked to find angle C.

AC is adjacent to angle C.

BC is the hypotenuse.

So we use the formula:

cos = adjacent / hypotenuse

cosC = 5/7

To calculate C we need to find the inverse of cos (INV cos or SHIFT cos):

C = Inv cos(5/7)

Using a calculator: C = 44.4°

Find the length of side BC.

Answer

We are given angle A and side AB.

AB is the hypotenuse.

BC is opposite angle A.

Therefore we use the formula:

sin = opposite / hypotenuse

sin 30 = BC / 7

Multiply both sides by 7

7 x sin30 = BC

Using a calculator we get

BC = 3.5cm